Inappropriate use of laboratory tests: How availability triggers demand - Examples across Europe.

INTRODUCTION: The appropriate use of laboratory diagnostics is increasingly at stake. The aim of this study was to depict some paradigmatic examples of under- and overutilization, as well as possible solutions across Europe. METHODS: We collected six examples from five European countries where a rise or decline of orders for specific laboratory parameters was observed after organizational changes but without evidence of changes in patient collective characteristics as source of this variation. RESULTS: The collected examples were the following: 1-Germany) Switch from a Brain-Natriuretic-Peptide assay to NT-pro Brain-Natriuretic-Peptide assay, resulting in a 374% increase in these analytics; 2-Spain) Implementation of a gatekeeping strategy in tumor marker diagnostics, resulting in a 15-61% reduction of these diagnostics; 3-Croatia) Stepwise elimination of creatine-kinase-MB assay from the laboratory portfolio; 4-UK) Removal of γ-glutamyl transferase from a "liver function" profile, resulting in 82% reduction of orders; 5-Austria) Implementation of a new device for rapid Influenza-RNA detection, resulting in a 450% increase of Influenza testing; 6-Spain) Insourcing of 1,25-(OH)2-Vitamin D measurements, leading to a 378% increase of these analyses. CONCLUSION: The six paradigmatic examples described in this manuscript show that availability of laboratory resources may considerably catalyze the demand, thus underscoring that inappropriate use of laboratory resources may be commonplace in routine laboratories all across Europe and most probably beyond. They also demonstrate that the application of simple strategies may assist in overcoming this issue. We believe that laboratory specialists need to refocus on the extra-analytical parts of the testing process and engage more in interdisciplinary patient-care.

Vitamin D in Follicular Fluid Correlates With the Euploid Status of Blastocysts in a Vitamin D Deficient Population.

Context: The widespread distribution of the Vitamin D (VitD) receptor in reproductive tissues suggests an important role for VitD in human reproduction. The assessment of patient´s VitD is based on the 25-hydroxyvitamin D (25(OH)D) metabolite measurement. However, most of the circulating 25(OH)D is bound to either VitD-binding protein (VDBP) (88%) or albumin (12%) and less than 1% circulates free. Objective: To determine a possible correlation between VitD levels in serum (S) and follicular fluid (FF) and blastocyst ploidy status in patients undergoing infertility treatment. Methods: A prospective observational study was performed including couples planned for preimplantation genetic testing for aneuploidies (PGT-A) from ART Fertility Clinics. Patients were classified according to their 25(OH)D-Serum levels: VitD deficient group <20 ng/ml and insufficient/replete ≥20 ng/ml defined as VitD non-deficient group. Results: Serum samples and 226 FF from individual follicles were collected for 25(OH)D, bioavailable 25(OH)D, free 25(OH)D, and % free 25(OH)D measurement. 25(OH)D-Serum in VitD deficient and non-deficient were 13.2±4.0 ng/ml vs 32.3±9.2 ng/ml; p<0.001. FF from 40 and 74 biopsied blastocysts was analysed of which 52.5 and 60.8% were euploid (p = 0.428), respectively. In VitD deficient patients, mean 25(OH)D-FF, bioavailable 25(OH)D-FF, and free 25(OH)D-FF were higher in euploid vs aneuploid blastocysts (18.3±6.3 ng/ml vs 13.9±4.8 ng/ml; p = 0.040; 1.5±0.5 ng/ml vs 1.1±0.4 ng/ml; p = 0.015; 0.005±0.002 ng/ml vs 0.003±0.001 ng/ml; p = 0.023, respectively), whilst no differences were found in VitD non-deficient patients (37.9±12.3 ng/ml vs 40.6±13.7 ng/ml; p = 0.380; 3.1±1.1 ng/ml vs 3.3±1.2 ng/ml; p = 0.323; 0.01±0.003 ng/ml vs 0.01±0.004 ng/ml; p = 0.319, respectively). Conclusion: VitD non-deficient patients have a significantly higher probability of obtaining a euploid blastocyst compared to VitD deficient patients (OR:33.36, p = 0.002).

Intervalos de referencia para 25-hidroxivitamina D en población autóctona y aparentemente sana de Yucatán / Reference values for 25-hydroxy-vitamin D in a native and apparently healthy population from Yucatan, Mexico

Introducción: La 25-hidroxivitamina D [25(OH)D] se considera un marcador del estado general de salud y su deficiencia es un problema a nivel mundial. En la actualidad no existe un consenso para definir sus niveles óptimos, siendo necesario establecerlos para cada población de acuerdo con sus características étnicas y factores ambientales a los que está expuesta. Objetivo: Determinar los intervalos de referencia para 25(OH)D en población autóctona y aparentemente sana de Yucatán. Métodos: Se estudiaron 71 voluntarios aparentemente sanos, de uno u otro sexo, de uno a 65 años, originarios y residentes en Yucatán. Se determinaron los niveles séricos de 25(OH)D, así como los de calcio, fósforo y paratohormona por su relación con el metabolismo de la vitamina D. Los intervalos de referencia se calcularon con los métodos paramétrico y consistente. Se registró el fototipo de piel y se aplicó el test de Garabédian para determinar el consumo diario de calcio y vitamina D. Resultados: El valor medio de 25(OH)D fue de 23,49±5,60ng/mL. Los límites de referencia para 25(OH)D total y por sexos fueron más estrechos y significativamente diferentes a los propuestos por el fabricante. Se encontró correlación directa entre los niveles de 25(OH)D y el calcio sérico (r=0,36; p=0,003) e inversa con la paratohormona intacta (r=−0,44; p<0,001). Una dieta rica en calcio y vitamina D no es suficiente para mantener los requerimientos normales de 25(OH)D en esta población. Conclusiones: Los intervalos de referencia propuestos están adecuados a las peculiaridades de la población de Yucatán, y pudieran mejorar la exactitud de la medición del estado de salud con base en los niveles séricos de vitamina D

Introduction: 25-hydroxyvitamin D [25(OH)D] is considered a marker of general health and its deficiency is a problem worldwide. There is still no consensus to define their optimal levels, with it being necessary to establish them for each population according to their ethnic characteristics and environmental factors to which they are exposed. Objective: To determine the reference intervals for 25(OH)D in the native and apparently healthy population of Yucatan. Methods:The study included 71 apparently healthy volunteers, female and male, between one and 65 years old, and originally from Yucatan. Serum levels of 25(OH)D were measured along with the determination of calcium, phosphorus, and parathormone levels due to their relationship with vitamin D metabolism. Reference intervals were calculated using parametric and robust methods. The skin phototype was recorded and the Garabedian test was applied to determine the daily intake of calcium and vitamin D. Results: The mean value of 25(OH)D was 23.49±5.60ng/mL. The reference limits for total and gender-related 25(OH)D, and by gender were narrower and significantly different from those proposed by the manufacturer. A direct correlation was found between 25(OH)D levels and serum calcium (r=0.36; P=.003) and an inverse one with intact parathormone (r=−0.44; P<.001). A diet rich in calcium and vitamin D is not sufficient to maintain the normal requirements of 25(OH)D in this population. Conclusions: The proposed reference intervals are adequate to the peculiarities of the population of Yucatan and could improve the accuracy of health status measurement based on serum levels of vitamin D

Development of a method for multiple vitamin D metabolite measurements by liquid chromatography coupled with tandem mass spectrometry in dried blood spots.

There are two forms of vitamin D which are essential to the human body, i.e. vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). The inactive metabolites of vitamin D are commonly used for quantitative analysis because of their longer half-life, stability, and relatively high blood concentrations. This paper presents the development of a high-throughput and sensitive method for determining four vitamin D metabolites in dried blood spots using liquid chromatography coupled with tandem mass spectrometry. This method allows for the determination of 25(OH)D2 and 25(OH)D3 concentrations, as well as the epimeric form 3-epi-25(OH)D3 and 24,25(OH)2D3. The analyzed material is capillary blood taken from the fingertip, deposited on filter paper. Four different chromatographic columns were tested to separate all compounds, in particular, the epimeric form. The column of choice was F5 (Phenomenex, Torrance, CA, USA). In order to prove the consistency between the results for DBS, used as an alternative biological matrix, and serum, comparative studies of these two materials were carried out in nearly 100 individuals. The results indicated their positive correlation. The evaluation of short-term stability of metabolites in DBS within the month showed no change in metabolite concentration. During the validation, the impact of the matrix on the ionization of the tested compounds was evaluated. Capillary blood and venous blood collected for different anticoagulants were also compared. The smallest differences in the results were obtained for citrate. In order to achieve a limit of quantitation of 0.2 ng ml-1, sample preparation involved derivatization using a Cookson-type reagent, 4-(4'-dimethylaminophenyl)-1,2,4-triazoline-3,5-dione (DAPTAD).

Niveles de vitamina D en pacientes con lesión medular traumática en Chile / Vitamin D levels in patients with traumatic spinal cord injury in Chile

Introducción. La vitamina D cumple un importante rol en el metabolismo óseo y en diversas funciones a nivel extraesquelético. El objetivo de este estudio es determinar la prevalencia de hipovitaminosis D en pacientes con lesión medular traumática (LMT) y describir su asociación con las características de la LMT y demográficas de los pacientes. Material y método. Estudio descriptivo prospectivo en 76 pacientes del Departamento de Rehabilitación del Hospital del Trabajador entre el 30 de julio 2015 y el 30 de julio de 2016. Se realizó la medición de 25-hidroxivitamina D (25-OH-D) en sangre mediante el método de radioinmunoanálisis y una encuesta estructurada a los pacientes. Los resultados se analizaron mediante estadística descriptiva, prueba de Kruskall Wallis, rangos signados de Wilcoxon, Chi cuadrado, Fisher y análisis de correlación de Spearman. Resultados. La mediana de la edad fue 49,5 años (±DE 15,05), el tiempo de evolución de LMT entre un mes hasta 36 años. El promedio de 25-OH-D fue 16,4ng/mL (4,2 - 45,9ng/mL). El 94,7% de los sujetos presentaban hipovitaminosis D (<30 ng/mL) y un 27,6% deficiencia severa (<10 ng/mL). No se encontraron diferencias significativas entre la asociación de hipovitaminosis con sexo, nivel y grado de compromiso de LMT, estación del año, tiempo de exposición al sol y zona donde habitan. Existe una correlación inversa con tendencia a disminuir los niveles de 25-OH-D por cada año de evolución de LMT (Ro=-0,33; p value=0,0040). Conclusión. La hipovitaminosis D es altamente prevalente en pacientes con LMT. Es importante diagnosticar oportunamente para su adecuada suplementación y disminuir la prevalencia de complicaciones (AU)

Introduction. Vitamin D plays an important role in bone metabolism and in various extra-skeletal functions. The aim of this study was to determine the prevalence of vitamin D deficiency in patients with traumatic spinal cord injury (TSCI) and to describe its association with the characteristics of TSCI and patients’ demographic characteristics. Material and method. A prospective descriptive study was conducted in 76 patients treated at the Rehabilitation Department of Hospital del Trabajador between July 30, 2015 and July 30, 2016. Blood measurement of 25-hydroxyvitamin D (25-OH-D) was performed by the radioimmunoassay method and a structured survey. The results were analysed using descriptive statistics, the Kruskall-Wallis test, Wilcoxon signed-rank test, chi-square test, Fisher test and Spearman rank correlation coefficient. Results. The median age was 49.5 years (SD 15.05) and the time from TSCI was between 1 month and 36 years. The mean 25-OH-D level was 16.4ng/mL (4.2-45.9ng/mL). Vitamin D deficiency (<30 ng/mL) was found in 94.7% of the participants and severe deficiency (<10ng/mL) in 27.6%. No significant differences were found between the association of vitamin deficiency with sex, neurologic level, or severity of TSCI, season, amount of time of sun exposure or geographical area of residence. There was s an inverse correlation with a tendency to decrease 25-OH-D for each year from the onset of TSCI (Ro=-0.33, p value=.0040). Conclusion. Vitamin D deficiency is highly prevalent in patients with TSCI. An early diagnosis is important to provide adequate supplementation in order to decrease the prevalence of complications (AU)

Update on Feline Ionized Hypercalcemia.

Hypercalcemia in cats is recognized with increased frequency, especially idiopathic hypercalcemia, which is the most common cause. Idiopathic hypercalcemia seems to be unique to the cat, not occurring in the dog as a specific syndrome. There are many causes of hypercalcemia, and diagnosis relies on evaluation of clinical signs, physical examination, diagnostic imaging, serum biochemistry, urinalysis, and evaluation of calcium metabolic hormones. With an accurate diagnosis, treatment options can be tailored to the individual.

Niveles de 25 hidroxivitamina D y riesgo cardiovascular en una cohorte de pacientes con enfermedad renal crónica avanzada / 25 hydroxyvitamin D levels and cardiovascular risk in a cohort of patients with chronic kidney disease

Introducción: Los niveles bajos de 25 hidroxivitamina D han sido relacionados con un aumento de la morbimortalidad de origen cardiovascular en la población general y en pacientes con enfermedad renal crónica. Objetivo: Nuestro objetivo fue estudiar los niveles de 25 hidroxivitamina D en un grupo de pacientes con enfermedad renal crónica estadios 4 y 5 prediálisis, y relacionarlos con los antecedentes de enferme- dad cardiovascular y con factores conocidos de riesgo cardiovascular. Material y métodos: Se trata de un estudio observacional transversal de una cohorte de 171 pacientes seguidos en la consulta prediálisis de nuestro hospital, me- dia de edad 64,16 ± 13 años, el 59,6% hombres, el 64,3% diabéticos, el 47,3% obesos y el 46,8% con antecedentes de enfermedad cardiovascular. A todos los pacientes se les mi- dieron los niveles séricos de 25 hidroxivitamina D y de 1-25 dihidroxivitamina D, se recogieron datos clínicos y analíticos de función renal, anemia, perfil lipídico y metabolismo óseo-mineral; también se evaluó la presión arterial mediante registro ambulatorio de 24 horas (MAPA) y se realizó estudio ecocardiográfico. Resultados: La media de los niveles de 25 hidroxivitamina D fue de 22,1 ± 13 ng/ml, sólo un 18,7% de los pacientes presentaban niveles normales, un 58,5% presentaban niveles insuficientes o bajos y un 22,8% niveles deficientes o muy bajos. Las variables que se asociaron con los niveles bajos de vitamina D fueron la edad, la diabetes, el sexo femenino, la obesidad, el filtrado glomerular y el antecedente de enfermedad cardiovascular. Dentro de los parámetros asociados a la presión arterial, la presión del pulso fue la que más se relacionó con los niveles de vitamina D. No se encontró asociación entre los niveles de 25 hidroxivitamina D con otros parámetros del metabolismo óseo mineral ni con los valores ecográficos de hipertrofia ventricular izquierda. En el análisis multivariante las variables que más se asociaron al déficit de 25 hidroxivitamina D fueron el sexo femenino, el antecedente de enfermedad cardiovascular, el filtrado glomerular y la presión del pulso del MAPA. Conclusiones: Nuestro estudio confirma una alta prevalencia de insuficiencia y deficiencia de 25 hidroxivitamina D en la población con enfermedad renal crónica avanzada; este déficit se asocia con la presencia de factores de riesgo cardiovascular y con el antecedente de enfermedad cardiovascular. Sin embargo, no se encontró ninguna asociación con uno de los principales predictores de eventos cardiovasculares como es la hipertrofia ventricular izquierda (AU)

Background: Decreased 25 hydroxyvitamin D serum levels have been related to an increase in cardiovascular morbility and mortality in both general population and chronic kidney disease patients. The aim of this study was to evaluate the relationship between 25 hydroxy vitamin D serum level, cardiovascular risk factors and previouses tablished cardiovascular disease in a group of patients with advanced chronic kidney disease. Material and methods: We performed a cross-sectional observational study in a cohort of 171 stage 4 and 5 chronic kidney disease out patients seen in our predialysis clinic, mean age64.16 ± 13 years, 59.6% were men, 64.3% had diabetes,47.3% had obesity, 46.8% had previous cardiovascular disease. 25 hydroxy vitamin D and 1-25 dihydroxy vitamin D were measured, we also determine other routine biochemical parameters. All subjects underwent anechocardiogram and 24 hours ambulatory blood pressure monitoring was also performed. Results: Mean 25hydroxyvitamin D levels were 22.1 ± 13 ng/ml, only 18.7%of the patients had adecuate levels, levels were insufficient in 58.5% of the patients and deficient in 22.8% of them. Low 25 hydroxyvitamin D levels were significatively related with age, diabetes, female gender, obesity, MDRD glomerular filtration rate and previous cardiovascular disease. Pulse pressure was the Ambulatory Blood Pressure Monitoring parameter that was better correlated with 25 hydroxyvitamin D levels. We could not find any association between vitamin D levels and other bone and mineral metabolism parameters. No relationship was seen between low vitamin D levels and left ventricular hypertrophy. On multivariate analysis lower levels of 25 hydroxyvitamin D were independently associated with female gender, previous cardiovascular disease, MDRD4-GFR and higher pulse pressure. Conclusions: Our study confirm a high prevalence of 25 hydroxyvitamin D insufficiency and deficiency in advanced chronic kidney disease patiens, this was associated with the presence of cardiovascular risk markers and previous established cardiovascular disease. However we could not see any relationship with left ventricular hypertrophy which is an known predictor of future cardiovascular events in this population (AU)

Diagnóstico y tratamiento de la deficiencia de vitamina D / Diagnosis and treatment of vitamin D deficiency

Nutritional status of vitamin D has regained importance in the last few years because its deficiency is highly prevalent, and because, apart from its well known effects on bone metabolism, this vitamin participates in cellular proliferation and differentiation and muscle strength and balance, among other effects. The active molecule is 1,25(OH)2D, but serum concentration of total 25 OH vitamin D (i.e. including ergocalciferol or vitamin D2 plus chole calciferol or vitamin D3) is the preferred indicator of vitamin D status. Recent evidences suggest the need to increase dietary recommendations in adults up to 1,000 IU/day. However, in deficiency states it is often necessary to supplement with pharmaceutical preparations, which contain higher doses of this vitamin since the amounts previously employed were not able to return levels to normal. In the present article we present the entire list of vitamin D preparations commercially available in Chile. The difficulty of choosing the most adequate product for an individual patient becomes clear, because there are only few formulations containing more than 800IU and, in addition they are usually combined with calcium, biphosphonates or multiple minerals and other vitamins.

El estado nutricional de vitamina D ha cobrado importancia en los últimos a±os debido a que su deficiencia es altamente prevalente, y además por sus conocidos efectos en el metabolismo óseo, participa en la diferenciación y proliferación celular, función muscular y equilibrio, entre otros. La molécula activa es la 1,25(OH)2D, pero se recomienda medir niveles séricos de 25 OH vitamina D total (es decir la suma de ergocalciferol o vitamina D2 y colecalciferol o vitamina D3), como reflejo del status de vitamina D. La evidencia actual sugiere la necesidad de elevar las recomendaciones para la ingesta dietaria en adultos, hasta cifras cercanas a 1.000 Ul/día. Sin embargo en casos de deficiencia puede ser necesario utilizar suplementos farmacéuticos conteniendo dosis superiores de esta vitamina, por cuanto aquellas utilizadas en el pasado no lograban corregir el déficit. En este artículo se presenta un listado de los preparados comerciales que contienen vitamina D disponibles en Chile. Al analizarlo se pone de mamfiesto la dificultad que representa elegir el preparado más adecuado para corregir la deficiencia en un paciente individual, debido a que son pocas las preparaciones que contienen más de 800 UI, además de que habitualmente se encuentra en asociación con calcio, bifosfonatos o múltiples otros minerales y vitaminas.

Evaluación diagnóstica y diagnóstico diferencial del hiperparatiroidismo primario / Diagnostic evaluation and differential diagnosis of primary hyperparathyroidism

El hiperparatiroidismo primario (HP) se caracteriza por la producción autónoma de parathormona (PTH), en el cual hay hipercalcemia o calcio sérico normal-alto, con valores séricos de PTH elevados o inapropiadamente “normales”. Excepcionalmente, en pacientes sintomáticos, el diagnóstico puede hacerse a partir de la sintomatología. El HP siempre debe cribarse en pacientes con historia de cálculos renales, nefrocalcinosis, dolor óseo, fracturas patológicas, resorción subperióstica o que presenten osteoporosis-osteopenia en densitometría ósea de doble fotón o con historia personal previa de irradiación en cuello o familiar de neoplasia endocrina múltiple tipo 1 o 2. El diagnóstico de HP es bioquímico. La hipercalcemia (calcio total corregido por albúmina), asintomática, sin signos ni síntomas guía, es la manifestación más frecuente de la enfermedad. Para el diagnóstico diferencial, además de la PTH1-84, debe medirse fósforo, cloro, 25-hidroxivitamina D, 1,25-dihidroxivitamina D y calciuria. La PTH1-84 suprimida, o inapropiadamente baja, orienta el diagnóstico a hipercalcemia tumoral y, de forma menos frecuente, a enfermedades granulomatosas (sarcoidosis, tuberculosis, etc.), toma inadecuada de calcitriol o 1α-hidroxivitamina D, intoxicación por vitamina D o A, toma de litio, endocrinopatías (hipertiroidismo, enfermedad de Addison, etc.), o tratamiento con tiazidas, entre otras. El diagnóstico de HP se confirma cuando hay hipercalcemia, o calcio en el rango normal-alto, en presencia de PTH1-84 alta o inapropiadamente normal, excepto si la excreción urinaria de calcio corregido por creatinina es menor de 0,01, en ausencia de toma de tiazidas, o deficiencia grave de vitamina D, que orienta el diagnóstico a la hipocalciuria hipercalcémica familiar. Las técnicas de imagen son útiles para localizar HP, pero no para su diagnóstico (AU)

Primary hyperparathyroidism (PHPT) is characterized by the autonomous production of parathyroid hormone (PTH), in which there is hypercalcemia or normal-high serum calcium levels, in the presence of elevated or inappropriately normal serum PTH concentrations. Exceptionally, in symptomatic patients, a diagnosis can be established on the basis of clinical data. PHPT must always be evaluated in patients with clinical histories of nephrolithiasis, nephrocalcinosis, osseous pain, subperiosteal resorption, and pathologic fractures, as well as in those with osteoporosis-osteopenia on dual-energy X-ray absorptiometry (DEXA), a personal history of neck irradiation, or a family history of multiple endocrine neoplasia syndrome (types 1 or 2). Diagnosis of PHPT is biochemical. Asymptomatic hypercalcemia (total serum calcium corrected by albumin), without guiding signs or symptoms, is the most frequent manifestation of the disease. For the differential diagnosis, PTH1-84 must be measured, as well as phosphate, chloride, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D and calcium-tocreatinine clearance. Suppressed or inappropriately low PTH1-84 guides the diagnose toward tumoral hypercalcemia and less frequently to granulomatous disease (sarcoidosis, tuberculosis, etc.), inadequate intake of 1α-hydroxyvitamin D or calcitriol, vitamin D or A intoxication, lithium intake, endocrinopathies (hyperthyroidism, Addison’s disease, etc.) or treatment with thiazides, among other possibilities. Diagnosis of PHPT is confirmed by demonstrating persistent hypercalcemia (or normal-high serum calcium levels) in the presence of inappropriately normal or elevated serum PTH1-84 concentrations, unless the urinary calcium-to-creatinine clearance ratio is lower than 0.01. In these cases, in the absence of thiazide intake or severe vitamin D deficiency, diagnosis should focus on benign familial hypercalcemic hypocalciuria. Parathyroid gland imaging is useful for localization of PHPT, but not for diagnosis of this entity (AU)

Niveles de 25-hidroxivitamina D en lactantes. Relación con la lactancia materna / 25-Hydroxyvitamin D levels in infants. Relation with breast-feeding

Objetivo: Determinar la prevalencia de la deficiencia subclínica de vitamina D en lactantes del área de Valencia, España (latitud 39,5° N) y su relación con la lactancia materna. Material y métodos: Se midieron los niveles séricos de calcio, fosfato, fosfatasas alcalinas, 25-hidroxivitamina D (25[OH]D) y hormona paratiroidea (PTH) intacta en 60 lactantes entre 1 y 6 meses de edad, nacidos a término (media de edad 3,9 meses), sin enfermedad ósea, gastrointestinal o renal (33 alimentados con lactancia materna exclusiva y 27 con lactancia artificial). Se recogieron datos de suplementación con vitamina D y de tiempo semanal de exposición solar. Resultados: Todos los lactantes tenían niveles normales de calcio, fosfato y PTH. En cinco de ellos (el 8,3 %), los niveles de 25(OH)D eran menores de 10 ng/ml (límite inferior de la normalidad). Todos ellos estaban alimentados con lactancia materna (el 15,1 % del grupo) y ninguno estaba suplementado con vitamina D. Los lactantes con hipovitaminosis D tenían ligeramente elevadas las fosfatasas alcalinas. Sólo el 48 % de los lactantes alimentados al pecho recibían habitualmente suplementos de vitamina D. La media de niveles de 25(OH)D en invierno del grupo con lactancia materna (16,8 ng/ml) fue significativamente más baja que la del grupo con alimentación artificial en verano (23,6 ng/ml; p < 0,05). Conclusiones: La asociación de escasa exposición al sol y ausencia de suplementación con vitamina D confiere a los niños con lactancia materna un alto riesgo para la deficiencia subclínica de vitamina D, incluso en regiones de clima templado

Objective: To determine the prevalence of subclinical vitamin D deficiency among infants in Valencia, Spain (latitude 39.5 degrees N) and its relation with breast- feeding. Material and methods: Serum levels of calcium, phosphate, alkaline phosphatase, 25-hydroxyvitamin D (25-OHD) and intact parathyroid hormone (PTH) were measured in 60 term infants aged between 1 and 6 months (mean age: 3.9 months), with no known bone, gastrointestinal or renal disease (33 exclusively breast-fed, 27 bottle-fed). Data on vitamin D supplementation and weekly direct sunlight exposure were also gathered. Results: All infants had normal serum calcium, phosphate and PTH levels. Five infants (8.3 %) had 25-OHD levels < 10 ng/ml (lower limit of normality) and all of these infants were breast-fed (15.1 % of the group). None of these five infants received vitamin D supplementation. Infants with vitamin D deficiency had slightly elevated serum alkaline phosphatase. Only 48 % of breast-fed infants received regular vitamin D supplementation. The mean serum 25-OHD concentration of breast-fed infants in winter (16.8 ng/ml) was significantly lower than that in bottle- fed infants in summer (23.6 ng/ml, p < 0.05). Conclusions: In breast-fed infants, the association of limited sunshine exposure and poor dietary vitamin D supplementation confers a high risk of subclinical vitamin D deficiency, even in regions with a temperate climate

The assessment of circulating 25(OH)D and 1,25(OH)2D: where we are and where we are going.

The field of Vitamin D assay technology has progressed significantly over the past 4 decades. Further, the clinical utility of these measurements has moved from esoteric into mainstream clinical diagnosis. This movement has been fueled by the realization that Vitamin D is involved in bodily systems beyond skeletal integrity. The clinical assay techniques for circulating 25(OH)D and 1,25(OH)(2)D have progressed away from competitive protein binding assay (CPBAs) that utilize tritium reporters to radioimmunoassay (RIAs) that utilize both I(125) and chemiluminescent reporters. These advances have allowed direct serum analysis of 25(OH)D in an automated format that provides a huge sample throughput. Detection of circulating 25(OH)D can also be achieved utilizing direct high-performance liquid chromatographic (HPLC) or liquid chromatography coupled with mass spectrometry (LC-MS) techniques. These methods are accurate, however, they require expensive equipment and restrict sample throughput in the large clinical laboratory. Direct serum detection of 1,25(OH)(2)D is unlikely to occur for many reasons as a sample pre-purification will always be required. However, a semi-automated chemiluminescent detection system with automated sample preparation is in final development for the determination of circulating 1,25(OH)(2)D. These advances will allow both 25(OH)D and 1,25(OH)(2)D to be detected in an accurate, rapid fashion to meet the clinical demands we see emerging.

Utilization of phytate and nonphytate phosphorus in chicks as affected by source and amount of vitamin D3.

Commercial and laboratory-strain crossbred chicks responded (P < .01) markedly to 1alpha-hydroxycholecalciferol (1alpha-OH D3) during the 2nd and 3rd wk of life. Bone-ash responses exceeded 50% when this compound was added at 20 microg/kg to phosphorus (P)-deficient corn-soybean meal diets containing surfeit levels (25 microg/kg) of cholecalciferol (D3). Phosphorus excretion was decreased (P < .01) and, thus, retention was increased (P < .01) when 1alpha-OH D3 was supplemented. A P-deficient (.10% P) casein-amino acid purified diet, devoid of D3, was used to determine whether 15 microg/kg of D3 was sufficient to facilitate optimal absorption of the nonphytate P contained in this diet. Bone ash responded to .075% P addition (KH2PO4), and chicks fed diets with .175% nonphytate P exhibited further bone-ash responses to 15 microg/kg of D3 or 10 microg/kg 1alpha-OH D3. Higher levels of either of these D3 compounds did not produce additional responses. This suggested that 15 to 25 microg/kg of D3 in a P-deficient corn-soybean meal diet (.28% phytate P and .14% nonphytate P) is more than adequate to facilitate optimal absorption of the nonphytate P present in the diet. A P-deficient casein-dextrose diet (.13% nonphytate P and 15 microg/kg D3) was fed in the final chick assay, and chicks fed this diet did not show bone ash responses to 1alpha-OH D3 or to microbial-derived phytase (1,470 units/kg). Thus, with P-deficient corn-soybean meal diets containing at least 15 microg D3/kg, 1alpha-OH D3 supplementation markedly increased weight gain and bone ash because it increased the utilization of phytate P.

Osteopenia in rheumatoid arthritis: a biochemical, hormonal and histomorphometric study.

To determine whether the osteopenia of rheumatoid arthritis (RA) is due to reduction of trabecular bone mass (TBV) and/or cortical width (CW), we evaluated these parameters by bone histomorphometry; we also measured the calciotropic hormones parathormone(PTH) and calcitonin (CT), vitamin D [25(OH)D] and the biological markers of bone remodeling in a group of patients with RA. Study subjects were divided into Group C - premenopausal patients, and Group A - menopausal patients and men of the same ages. These groups were compared to two age-matched control groups, B and D. In both A vs. B and C vs. D, TBV and CW were significantly lower in patients. There were no differences in PTH or CT, but 25(OH)D was significantly reduced, and BGP, OHP/Cr and AP were raised in patients. Patients also exhibited TBV loss in more than 55% and CW loss in more than 98%. These changes suggest that the decline in bone mass, mainly cortical, but also trabecular, is due to increased bone turnover and enhanced resorption and seem to reflect intrinsic alterations of RA.

25-Hydroxyvitamin D and vitamin D in human milk: effects of supplementation and season.

Breast-milk 25-hydroxyvitamin D (25-[OH]D) and vitamin D were measured in mothers supplemented with 2000 or 1000 IU (50 or 25 micrograms) of vitamin D/d or with no supplementation. Fore- and hindmilk samples were collected at two stages of lactation (8 and 15 or 20 wk after delivery) and at different seasons. Season affected the levels of 25-(OH)D and vitamin D. The 25-(OH)D levels were higher in hind- than in foremilk. Supplementation had no effect on vitamin D levels. Milk 25-(OH)D levels of mothers receiving either 1000 or 2000 IU (25 or 50 micrograms) vitamin D/d were significantly higher than those of unsupplemented mothers in February and April. In theory, supplementation with 2000 IU (50 micrograms) vitamin D should have increased the calculated antirachitic activity of the milk in winter to the levels of unsupplemented mothers in September; however, responses varied widely among individuals.

Increased 25-hydroxyvitamin D levels in portal blood following cholecystokinin injection in the dog.

To establish whether an enterohepatic circulation of the metabolites of vitamin D exists, polyethylene catheters were cannulated into the portal vein of dogs. The dogs were then starved for 24 h and injected with cholecystokinin (CCK) to induce gall bladder contraction. At various time intervals thereafter blood samples were collected from the portal and the saphena veins, and sera prepared and analyzed for the metabolites of vitamin D. The serum levels of 25-hydroxyvitamin D [25(OH)D] were found to be significantly higher in the portal blood when compared with levels in peripheral blood following CCK injection. Since portal blood collects nutrients absorbed from the gut and as the dogs were starved for 24 h prior to blood collection, the only source of the increased concentrations of 25(OH)D in portal blood is likely to be bile. These findings support the notion that an enterohepatic circulation of 25(OH)D does exist under normal physiological conditions.

Validation of liquid chromatographic method for assay of calcitriol and alfacalcidol in capsule formulations.

The validation of a liquid chromatographic procedure suitable for the determination of calcitriol and alfacalcidol in their respective formulations labeled to contain at least 0.25 micrograms drug per unit is described. The capsule content is diluted and chromatographed in 15-20 min on silica columns (5 micron) with a mobile phase of hexane-tetrahydrofuran-methylene dichloride-isopropanol (72 + 12 + 12 + 4, v/v) with detection at 254 nm. The calibration curve is linear. Recoveries of "spikes" averaged 101% with a standard deviation of 2%. Precision was better than 1.5%.

Relationships among vitamin D, 25-hydroxyvitamin D, and vitamin D-binding protein concentrations in the plasma and milk of human subjects.

We measured plasma and milk concentrations of vitamin D2, vitamin D3, 25-hydroxyvitamin D2 (25OHD2), 25-hydroxyvitamin D3 (25OHD3), and vitamin D-binding protein (DBP) in a group of lactating women. All vitamin D compounds were quantitated using competitive protein binding assay, while DBP concentrations were determined by rocket electrophoresis. Vitamin D3 was the most abundant vitamin D compound in human milk, followed by vitamin D2, 25OHD3, and, finally, 25OHD2. The average vitamin D activity in milk was between 33-68 IU/liter, depending on the criterion of biological activity used. DBP concentrations in milk were approximately 3% of those in plasma. Significant relationships were found between plasma and milk levels for all vitamin D compounds. The milk to blood concentration ratio was greatest for vitamin D2, followed by vitamin D3, 25OHD2, and 25OHD3. (Thus, the parent compounds gained access into milk in a much more efficient fashion than their 25-hydroxy metabolites. It is postulated that this differential translocation is controlled by the DBP in the circulation.) There was no significant correlation between plasma and milk DBP concentrations, nor were milk DBP concentrations related to the vitamin D content of milk. This investigation supports the concept that the nutritional status of lactating mothers affects the vitamin D sterol potential of her milk which, in turn, would likely have an effect on the vitamin D status of her nursing infant.

[Vitamin D sterol in human milk, cow's milk and baby food]. / Vitamin-D-Sterole in Frauenmilch, Kuhmilch und Säuglingsnahrung.

A review is given of the results of vitamin D determinations in human and cow's milk using physico-chemical methods. Thereby only parent vitamin D is determined. Further, the results obtained with protein-binding assays are discussed in detail. With the aid of these newer methods the concentrations of hydroxylated vitamin D derivatives can also be measured. A comparison of the concentration of these vitamin D metabolites in human milk and infant formulas based upon cow's milk suggests that the higher anti-rachitic activity of human milk is connected with its higher concentration of 25-hydroxy-vitamin D.