Potentially inappropriate testing for vitamin D deficiency: a cross-sectional study in Switzerland.

BACKGROUND: There is consensus that vitamin D supplementation is often indicated but population-based screening by laboratory testing for vitamin D deficiency is inadequate. Testing should be restricted to people at high risk of severe deficiency. This study describes the current lab testing for vitamin D deficiency in the adult population of Switzerland. METHODS: We assessed Swiss health insurance data (SWICA) for incidence of lab testing for vitamin D levels, comparing the years 2015 and 2018. Claims were analyzed for associations between lab testing and age, sex, medical indications, insurance status and geographic location in multivariable regression analyses. We also estimated the costs of vitamin D testing. RESULTS: Data from 200,043 and 200,046 persons for 2015 and 2018, respectively, were analyzed. Vitamin D level was tested in 14% of the sample population in 2015 and 20% in 2018. Testing increased by 69% for individuals aged 26-30. Testing was associated with being middle-aged to young senior citizens, female, medical indications (pregnancy, renal disease, osteoporosis, hyperparathyroidism, HIV, glucocorticoid intake), more chronic conditions, having a mandatory insurance with a low deductible, additional insurance coverage, and living in urban areas. We estimate that the total laboratory cost to mandatory insurance was about 90 million Swiss francs in 2018. CONCLUSIONS: Despite recommendations for routine vitamin D supplementation, vitamin D testing of low risk individuals is common and increasing in Switzerland.

[Appropriate use of vitamin D assessments in primary health care: Impact of new strategies for the introduction and follow-up of analyses in Östergötland]. / D-vitaminanalyser i primärvård måste användas ändamålsenligt - Ny strategi i Östergötland för införande och uppföljning av analyser gav bra resultat.

Systematic reviews and meta-analyses have shown that there is little justification for vitamin D supplements to prevent infections, cancer and cardiovascular disease. Despite the limited evidence of effectiveness, the total number of ordered serum 25-hydroxyvitamin D (25(OH)D) tests has increased considerably in recent years. There seems to be an overuse of this test that does not provide meaningful benefit for patients. A passive introduction of new tests leads generally to a slow initiation of value-based diagnostics, as well as overuse and underuse of diagnostic tests. In this study, in Region Östergötland, we applied a ¼Choosing wisely« model that reversed a rising trend of 25(OH)D tests and reduced the number of unnecessary tests. The findings point to the need for strategic plans for introducing new analyses and approaches to counteract misuse of laboratory diagnostics. We recommend ¼Choosing wisely« models for the introduction of new analyses to facilitate appropriate laboratory diagnostics and to counteract long-term overuse.

Protein S testing in patients with protein S deficiency, factor V Leiden, and rivaroxaban by North American Specialized Coagulation Laboratories.

In 2010-2012, the North American Specialized Coagulation Laboratory Association (NASCOLA) distributed 12 proficiency testing challenges to evaluate laboratory testing for protein S (PS). Results were analysed to assess the performance of PS activity, PS free antigen, and PS total antigen testing. Statistical analysis was performed on the numeric results and qualitative classification submitted for each method. There were 2,106 total results: 716 results from PS activity assays, 833 results from PS free antigen assays, and 557 results from PS total antigen assays. The three assay types performed well in the classification of five normal samples and nine abnormal samples, although certain PS activity methods were more likely to classify normal samples as abnormal and one PS total antigen assay was more likely to classify abnormal samples as normal. PS activity methods were affected by interfering substances such as heterozygous or homozygous factor V Leiden mutation (underestimation) and the anticoagulant drug rivaroxaban (overestimation). In conclusion, NASCOLA laboratories using a variety of PS assays performed well in the classification of clearly normal and abnormal samples. Laboratories performing PS activity assays should be aware of potential interferences in samples positive for FV Leiden or containing certain anticoagulant medications.

Serum magnesium levels in pediatric inpatients: a study in laboratory overuse.

BACKGROUND AND OBJECTIVE: Hypomagnesemia, defined as a serum magnesium (Mg) level<1.5 mg/dL (0.62 mmol/L), is often asymptomatic. The goals of this study were to determine the incidence of clinically significant abnormal Mg levels in the inpatient setting and to identify diagnoses for which testing would be diagnostically helpful. METHODS: We obtained data from 2010 through 2011 on charges for serum Mg levels and Mg supplementation for all non-ICU inpatients from the 43 tertiary care children's hospitals in the Pediatric Health Information System database. A manual chart review was performed for all patients at our institution with charges for both Mg levels and Mg supplementation. RESULTS: A median of 13.5% (interquartile range: 7.7-22.1) of non-ICU inpatients from Pediatric Health Information System centers had charges for Mg levels, at a total charge of $41 million in the 2010-2011 period. At our institution, 19.1% of non-ICU inpatients had charges for Mg levels, at a charge of $67.32/patient-day. Of the 4608 patients with Mg laboratory charges at our institution, 171 (3.7%) had an intervention, defined as addition or modification of an Mg supplement dose in response to a serum Mg level. The 4 most common groups of diagnoses (oncologic, abdominal surgery requiring total parenteral nutrition, solid organ transplant, and short bowel syndrome) accounted for 143 (83.6%) of these interventions. CONCLUSIONS: Serum Mg levels were frequently ordered in non-ICU inpatients, but levels were seldom abnormal and rarely resulted in changes in clinical management. These findings raise concerns about resource overutilization and provide a target for more judicious laboratory ordering practices.

Variability and reproducibility of circulating vitamin D in a nationwide U.S. population.

CONTEXT: Most studies examining associations between circulating vitamin D and disease are based on a single measure of vitamin D, which may not reflect levels over time, particularly because vitamin D concentrations vary by season. Few studies evaluated how well multiple 25-hydroxyvitamin D [25(OH)D] measures track within the same individual over time. OBJECTIVE: This study examined variability and reproducibility of vitamin D by evaluating repeat measurements of plasma 25(OH)D concentrations while accounting for determinants of circulating concentrations including dietary supplement use and latitude of residence from a population of U.S. radiologic technologists. DESIGN AND PARTICIPANTS: We analyzed circulating 25(OH)D in blood samples taken from 538 men and women from a prospective, nationwide study at two time points within a 1-yr period, most measured in different seasons. Inter- and intra-individual variability, reliability coefficients, and measurement error were examined. RESULTS: The spearman rank correlation between two measurements of 25(OH)D concentrations was moderate (r = 0.75, P < 0.001) and did not vary significantly by participant characteristics including age, race, or latitude. The intraclass correlation coefficient was 0.72 (95% confidence interval = 0.68-0.76). The deattenuation factor of plasma 25(OH)D levels was 1.39, suggesting that a single measure of vitamin D on a continuous scale in regression analyses may result in attenuated relationships of about 40%. CONCLUSION: Our results suggest that a single blood sample obtained in spring or fall provides a reasonable average for 25(OH)D over a 1-yr period, but additional studies are needed to estimate variability and agreement in plasma 25(OH)D measurements over longer intervals and younger populations.

Frequency of laboratory measurement and hyperkalaemia in hospitalised patients using serum potassium concentration increasing drugs.

PURPOSE: Although, drug-drug interactions (DDIs) between potassium-increasing drugs (PIDs) are known risk factors for developing hyperkalaemia, not much is known about their risk and management strategies during hospitalisation. This study examines the frequency of serum potassium measurements and hyperkalaemia in hospitalised patients, based on the use of one or more PIDs, and the determinants thereof. METHODS: Adult patients hospitalised in the University Medical Centre Utrecht between 2006 and 2008 were included in this cross-sectional study. The frequency of serum potassium measurements and of hyperkalaemia were compared between patients using only one PID at a time (monotherapy group) and patients using two or more PIDs concomitantly (interaction group). The determinants studied were renal failure, diabetes mellitus, use of diuretics, type of DDI, start of the PIDs within the hospital versus continued home medication and medical speciality. RESULTS: Serum potassium was measured more frequently in the interaction group than in the monotherapy group [67 vs. 56%; relative risk (RR) 1.19, 95% confidence interval (CI) 1.14-1.24] and the risk of hyperkalaemia was also increased in the interaction group (9.9 vs. 5.9%, RR 1.7, 95% CI 1.3-2.1). The combination of potassium-sparing diuretics plus a potassium supplement, start of the PID within the hospital and hospitalisation in non-internal medicine departments was associated with higher relative risk estimates for hyperkalaemia. CONCLUSIONS: Among our patient cohort, even when physicians received a direct pop-up to monitor serum potassium levels when prescribing two PIDs concomitantly, serum potassium levels were not measured in 33% of patients, and 10% of patients developed hyperkalaemia. Improved management strategies and/or clinical decision-support systems are needed to decrease the frequency of hyperkalaemia following DDIs.

High performance liquid chromatography for the determination of glucosamine sulfate in human plasma after derivatization with 9-fluorenylmethyl chloroformate.

In this study, we developed a simple, rapid, sensitive, and reliable method for the determination of glucosamine sulfate in human plasma, which was based on derivatization with 9-fluorenylmethyl chloroformate (FMOC-Cl) followed by reverse-phase HPLC-FLD. For the first time, FMOC-Cl was introduced into derivatization of glucosamine sulfate in human plasma. The amino groups of glucosamine sulfate and vertilmicin sulfate (the internal standard) were trapped with FMOC-Cl to form glucosamine-FMOC-Cl and vertilmicin-FMOC-Cl adducts, which can be very suitable for HPLC-FLD. Precipitation of plasma proteins by acetonitrile was followed by vortex mixing and centrifugation. Chromatographic separation was performed on a C18 column (DIAMONSIL 150 x 4 mm id, 5 microm) with a mobile phase gradient consisting of acetonitrile and water at a flow-rate of 1 mL/min. The retention times of glucosamine-FMOC-Cl and vertilmicin-FMOC-Cl adducts were 8.9 and 21.2 min, respectively. This method was shown to be selective and sensitive for glucosamine sulfate. The limit of detection was 15 ng/mL for glucosamine sulfate in plasma and the linear range was 0.1-10 mg/mL in plasma with a correlation coefficient (r) of 0.9999. The relative standard deviations (RSDs) of intra-day and inter-day assays were 5.2-8.1% and 6.1- 8.5%, respectively. Extraction recoveries of glucosamine sulfate in plasma were greater than 90%. The validated method was successfully applied to the determination of glucosamine sulfate in human plasma samples.

[Importance of the "adequate blood phosphorus" concept as a risk factor for hyperphosphatemia]. / Importancia del concepto "fosfatemia adecuada" como factor de riesgo de hiperfosfatemia.

Hyperphosphatemia is an important risk factor of secondary hyperparathyroidism and extraosseous calcifications in chronic renal failure patients. In this study our hypothesis is that physicians misconception of adequate phosphatemia is a risk factor for hyperphosphatemia. In 1999 GEMOR sent a renal osteodystrophy inquiry to different hemodialysis centers in Argentina. It included 80 dialysis centers in 17 Argentinian provinces. The enquire had 33 questions about renal osteodystrophy. Here we report the section related to phosphorous metabolism. We obtained responses from 80 dialysis centers (4,512 dialysis patients), which represents about 24% of Argentinian dialysis centers. Physicians considered phosphorous levels between 4.5 to 5.5 mg/dl in 83.5% of centers as adequate, and between 5.5 to 6.5 mg/dl in 10.1%. Five out of 77 centers reported that they had no patients with hyperphosphatemia. The percentage of hemodialysis patients that had more than 6 mg/dl in each center was 28.8 +/- 15.9%. Those centers that aimed for phosphatemia between 5.5 and 6.5 mg/dl, had a higher percentage of patients with phosphatemia above 6 mg/dl than those aiming for between 4.5 and 5.5 mg/dl (42.8 +/- 16.7 vs 27.1 +/- 15.2% respectively, p = 0.007), and had higher mean of phosphatemia (6.4 +/- 0.7 vs 5.3 +/- 0.7 mg/dl respectively, p = 0.0001), than the last group. In conclusion, a higher mean phosphate level was obtained in hemodialysis centers where physicians considered higher pre-dialysis target levels. Some centers had no patients with hyperphosphatemia (neglect or good control?).

Calcium, magnesium, and phosphorus: emergency department testing yield.

OBJECTIVES: To investigate how often the ED ordering of stat serum calcium (Ca+2), magnesium (Mg+2), and phosphorus (PO4(-3)) levels affected clinical treatment; to define the diagnoses of patients for whom Ca+2, Mg+2, and PO4(-3) measurements did affect clinical therapy; and to suggest guidelines for more appropriate ordering of these laboratory tests. METHODS: A retrospective chart review was performed in an academic teaching hospital. All adult ED patients who had Ca+2, Mg+2, or PO4(-3) laboratory testing during the 9-month study period were included and evaluated for potential clinical impact of an abnormal Ca+2, Mg+2, or PO4(-3) laboratory test. RESULTS: 1.477 patients had Ca+2, Mg+2, or PO4(-3) measured while in the ED during the study period. Of these, 260 patients (17.6%) had a total of 312 abnormal Ca+2, Mg+2, or PO4(-3) values as defined by results exceeding +/- 15% of normal reference values. Of these, only 5 patients (0.3%) received treatment for abnormal values in the ED, while 75 patients (5.1%) were treated once admitted to the hospital. In this study, the only diagnostic groups to whom significant treatment was administered were diabetic patients (Ca+2 and PO4(-3); alcoholic patients (Mg+2); and renal failure patients (Ca+2, Mg+2, and PO4(-3). CONCLUSION: These results suggest that stat Ca+2, Mg+2, and PO4(-3) levels seldom affect clinical treatment in the ED. The frequency of ordering these tests may be reduced by obtaining Ca+2, Mg+2, or PO4(-3) measurements only for patients known to be at risk for such abnormalities, based on their existing or suspected diagnoses. The authors suggest obtaining these tests, when indicated, on a "non-stat" basis, with the subsequent laboratory results becoming available in-hospital, where treatment is more likely to occur.

Determination of serum oxalate using peroxyoxalate chemiluminescence of free oxalic acid.

We describe a new sensitive and specific method for determination of oxalate in human serum. By using the chemiluminescence decay of monoperoxyoxalic acid very low concentrations of oxalate (200 nmol/L) can be determined. The mean serum oxalate level in apparently healthy controls was 14.5 +/- 8.5 mumol/L. Supplementation of ascorbic acid leads to an increase in serum oxalate level. While serum oxalate concentrations of calcium oxalate stone formers (x = 16.4 +/- 9.8 mumol/L) are not significantly different from the control group, an extreme increase of serum oxalate is evident in haemodialysis patients. The serum oxalate concentration decreased during dialysis treatment from 141.4 +/- 32.1 mumol/L to 36.4 +/- 12.7 mumol/L.

Efficacy of preadmission testing in ambulatory surgical patients.

A retrospective study was done with 325 patients who had preadmission testing prior to ambulatory surgery. At least one laboratory abnormality was noted in 84% of the patients. The serial multiple analysis (SMA)-7 was abnormal 63% of the time. Abnormalities were seen in 54% of the SMA-12 panels and 38% of the urinalyses performed. Twenty-four percent of the patients treated had an abnormal electrocardiogram (ECG). An abnormal chest roentgenogram was found in 19% of the patients. Only three (1%) patients potentially benefited from preadmission testing. Ninety-six percent of the abnormal laboratory results were ignored by the attending physicians. Therefore, we conclude that preadmission testing should be done on a selective basis. Patients older than 50 years of age should have an ECG. A hematocrit should be obtained only if major blood loss is anticipated. All other tests should be ordered based on the history and physical examination.