Beyond the bias! Sex distribution in paediatric growth hormone deficiency reexamined.

OBJECTIVES: Various biases pertaining to stature account for a male sex predominance in growth hormone deficiency (GHD) cases diagnosed by endocrinology clinics. This manuscript will assess the sex distribution when biases are minimised. METHODS: Retrospective chart review was conducted on patients diagnosed with GHD between 3 and 16 years of age. The sex distribution of cases was ascertained according to: (1) peak GH (pGH) by groups; based on growth hormone provocative testing, (2) pituitary gland imaging results, and (3) isolated GHD (IGHD) versus multiple pituitary hormone deficiencies (MPHD). The relative frequency of each sex was compared according to these subgroups with significance evaluated at α = .05 level. RESULTS: Of the 5880 clinic referrals for short stature, there were 3709 boys (63%) and 2171 girls (37%). Of these, 20% of boys (n = 745) and 15.3% of girls (n = 332) underwent provocative testing for GHD. Of those tested, 39.2% of boys (n = 292) and 32.2% of girls (n = 107) were diagnosed with GHD, all p < .001. There was a male predominance in GHD cases based on pGH or GHD severity. Though not significant, girls were more likely than boys to have MPHD (p = .056), even across pGH groups (p = .06). Both boys and girls had a similar distribution of imaging abnormalities. CONCLUSION: Stratifying by sex, we found similar percentages of pituitary imaging abnormalities (including tumours) and the number of pituitary hormone deficiencies in boys and girls as the cause of GHD. For these classifications, we did not find the historically reported male sex predominance.

Lead poisoning: Clinical and laboratory considerations.

Lead has been a known source of toxicity for millennia due to widespread use until the 20th century. Consequently, there remains significant, though decreasing, exposure to lead throughout the world. Clinical signs and symptoms of lead toxicity are well-documented but is particularly concerning for children six years of age and under, as brain development is rapid and therefore, is likely to be affected by even low levels of lead. Therefore, in the United States, it is recommended that young children to be routinely screened for blood lead levels. Blood lead levels can be measured by various methods in laboratories with blood collection greatly impacting possible lead contamination of samples. The history, presentation, and laboratory testing methodologies will be discussed.

The utility of a random cortisol level in determining neonatal central adrenal insufficiency.

OBJECTIVES: While it has been established within the first 4 months of life that there is no circadian rhythm, what is unclear is the usefulness of a random serum cortisol (rSC) level in determining neonatal central adrenal insufficiency (CAI). The objective of the study is to determine the utility of using rSC in infants less than 4 months old in the evaluation of CAI. DESIGN AND PATIENTS: Retrospective chart review of infants who underwent a low dose cosyntropin stimulation test ≤4 months of life with rSC taken as baseline cortisol before stimulation. Infants were divided into three groups: those diagnosed with CAI, those at risk for CAI (ARF-CAI) and a non-CAI group. Mean rSC for each group was compared, and ROC analysis was used to identify rSC cut-off for the diagnosis of CAI. RESULTS: Two hundred and fifty one infants with the mean age of 50.5 ± 38.08 days, and 37% of these were born at term gestation. The mean rSC were lower in the CAI group (1.98 ± 1.88 mcg/dl) as compared to the ARF-CAI (6.27 ± 5.48 mcg/dl, p = .002) and non-CAI (4.6 ± 4.02 mcg/dl, p = .007) groups. ROC analysis identified a cut-off of rSC level of 5.6 mcg/dL is associated with 42.6% sensitivity and 100% specificity for the diagnosis of CAI in term infants. CONCLUSIONS: This study demonstrates that though an rSC can be used within the first 4 months of life, its value is best when done ≤30 days of life. Moreover, a diagnostic cut-off for CAI using rSC levels was identified for term infants.

Routine sample transportation of centrifuged barrier tubes impacts certain chemistry analytes.

The preanalytical phase of testing, including sample transportation, is a common source of error in laboratory testing. Previous studies have shown inversion of centrifuged plasma separator tubes (PST) results in elevation in certain analytes. However, it remains unclear if routine transportation practices, without full inversion, can have a similar impact. This study used 12 residual samples submitted in PST and 4 PST tube samples collected from healthy donors. All samples were measured at baseline. Analytes measured were white blood cells (WBCs), red blood cells (RBCs), platelets (PLTs) using the Sysmex XN-1000 and potassium (K), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), sodium (NA), and alanine aminotransferase (ALT) using the Ortho Vitros 4600. The samples were split into two groups: 1 group was placed vertically in racks and the other group were laid horizontally in a messenger bag-style soft-sided cooler used by lab couriers. A cold pack was placed in the bag, equidistant from both groups of samples. To mimic courier transportation, the bag was carried for 30 min, returned to the laboratory and immediately analyzed. Subsequently, the samples were re-centrifuged and analyzed again. Statistics were performed using GraphPad Prism. LDH increased following transportation for vertical and horizontal samples and remained elevated despite re-centrifugation. K was only increased in the horizontal samples following re-centrifugation. Notably, AST as well as WBCs, RBCs, and PLTs all increased following transportation, but dropped to baseline concentrations following re-centrifugation. Centrifuged PSTs should be kept in a vertical position during transportation by courier. Re-centrifugation of plasma gel tubes after transportation may be necessary for certain chemistry tests.

Current State of Pediatric Reference Intervals and the Importance of Correctly Describing the Biochemistry of Child Development: A Review.

Importance: Appropriately established pediatric reference intervals are critical to the clinical decision-making process and should reflect the physiologic changes that occur during healthy child development. Reference intervals used in pediatric care today remain highly inconsistent across a broad range of common clinical biomarkers. Observations: This narrative review assesses biomarker-specific pediatric reference intervals and their clinical utility with respect to the underlying biological changes occurring during development. Pediatric reference intervals from PubMed-indexed articles published from January 2015 to April 2021, commercial laboratory websites, study cohorts, and pediatric reference interval books were all examined. Although large numbers of pediatric reference intervals are published for some biomarkers, very few are used by clinical and commercial laboratories. The patterns, extent, and timing of biomarker changes are highly variable, particularly during developmental stages with rapid physiologic changes. However, many pediatric reference intervals do not capture these changes and thus do not accurately reflect the underlying biochemistry of development, resulting in significant inconsistencies between reference intervals. Conclusions and Relevance: There is a need to correctly describe the biochemistry of child development as well as to identify strategies to develop accurate and consistent pediatric reference intervals for improved pediatric care.

Use of Cotton Balls in Diapers for Collection of Urine Samples Impacts the Analysis of Routine Chemistry Tests: An Evaluation of Cotton Balls, Diapers, and Chemistry Analyzers.

OBJECTIVE: To evaluate the suitability of urine samples collected with cotton balls placed into diapers for routine laboratory chemistry analyses. STUDY DESIGN: Twenty pools of residual unpreserved urine samples were separated into control and treated aliquots. The treated samples were absorbed into 2 different brands of cotton balls, wrapped in 3 different brands of diapers, and incubated at 37°C for 1 hour. The urine-soaked cotton balls were placed into a syringe and expressed via plunger depression. Urine sodium, potassium, creatinine, urea, calcium, magnesium, inorganic phosphorus, albumin, and total protein were measured on all samples on 5 automated clinical chemistry platforms: Ortho Vitros 4600, Siemens Dimension Vista 500, Beckman Coulter AU5822, Roche Cobas 6000, and Abbott Architect c8000 at 5 separate hospital laboratories. Criteria used to exclude the presence of significant effects of urine from presoaked cotton balls in a diaper on the measurement of chemistry laboratory tests were R2 >0.95, slope of 0.9-1.1, and mean bias within ±10%. RESULTS: Albumin and total protein measurements demonstrated significant negative bias in urine from both brands of presoaked cotton balls with all brands of diapers on all 5 chemistry platforms compared with the control urine. We did not observe a significant effect of presoaking urine in cotton balls in a diaper on the measurement of sodium, inorganic phosphorus, and urea. The remaining tests demonstrated significant effects when measured in urine from presoaked cotton balls and/or diapers that were specific to the chemistry analyzer platform or diaper. CONCLUSIONS: Diaper and cotton ball-based urine collection significantly impacts the measurement of several common chemistry assays.

The necessity of magnetic resonance imaging in the evaluation of pediatric growth hormone deficiency: Lessons from a large academic center.

BACKGROUND: Current guidelines indiscriminately recommend magnetic resonance imaging (MRI) of the pituitary gland in pediatric growth hormone deficiency (GHD). The relationship between abnormal MRI, most importantly a tumor, and peak GH levels is not well known. METHODS: In this retrospective chart review, pituitary MRI results of children, ages of 3-16 years with GHD were collected and divided into 3 groups according to peak stimulated GH levels; ≤5, 5-7.4 and 7.5-10 ng/mL, Groups A, B & C respectively. Clinical and MRI findings were compared between the groups. RESULTS: A total of 399 children were included. Abnormal MRI was found in 36.9% of group A subjects, compared to group B (16.7%) and group C (17.0%), both p values =0.0002. Children with multiple pituitary hormonal deficiencies (MPHD) had a higher rate of abnormalities than those with isolated GHD. Children with isolated GHD were more likely to have abnormal MRI with peak GH level < 5 ng/mL compared to those with levels, 5-7.4 & 7.5-10 ng/mL. 4 children in group A had a craniopharyngioma. ROC analysis comparing peak GH levels with abnormal MRI findings showed an area under the curve (AUC) of 0.614 and 0.728 for IGHD and MPHD, respectively. CONCLUSION: Although abnormal MRI was found in all 3 study groups, it was more likely at GH level < 5 ng/mL and in children with MPHD. To avoid missing a tumor, the importance of imaging in children with GHD and peak GH levels <5 ng/mL cannot be overemphasized.

The Effect of Urine Collection with a Novel External Catheter Device on Common Urine Chemistry and Urinalysis Results.

INTRODUCTION: Urine collection from incontinent individuals can be challenging. Various methods have been devised to collect the sample without catheterization. Recently the PureWick external catheter was developed to draw the sample gently away from external female genitalia. While the primary purpose of the device is to prevent moisture and maintain skin integrity, the urine that is collected may be sent for laboratory analysis. We sought to validate the use of this collection method for common urine chemistry assays and urinalysis. METHODS: Twenty pools of residual urine samples were separated into "control" and "PureWick" treated samples. The control samples were maintained at room temperature while 15 mL of urine was added to the PureWick device which was connected to a vacuum line through a collection canister. The urine collected in the canister and the controls samples were all subject to urine chemistry strip, microscopic, and automated urine chemistry analysis. Results were compared between pairs of treated and control samples. RESULTS: No clear affect was noted on urine strip semi-quantitative or automated chemistry analysis from the PureWick collection. There was a statistically significant decrease in microscopic measurements of white blood cells and crystals in the PureWick urine samples. DISCUSSION: This study supports the use of the PureWick external catheter for collection of samples for most urinalysis and urine chemistry tests.

The utility of a random growth hormone level in determining neonatal growth hormone sufficiency.

BACKGROUND: Random growth hormone (GH) levels have been used in the neonate to investigate congenital growth hormone deficiency (GHD). The cut-off value for use in this diagnosis is yet to be established. METHODS: This is a retrospective chart review of all random GH levels obtained in neonates ≤28 days of age. Neonates were divided into three groups: those diagnosed with congenital GHD, those at risk for GHD (ARF-GHD) and a non-growth hormone deficient (non-GHD) group. Mean GH levels for each group were compared, and ROC analysis was used to identify a cut-off for the diagnosis of GHD. RESULTS: The study included 138 neonates with the mean age of 9.07 ± 6.6 days, and 65% of these were born at term gestation. Mean GH levels were lower in the GHD group (2.73 ± 1.19 ng/ml) as compared to the ARF-GHD (9.4 ± 7.96 ng/ml, p = .002) and non-GHD groups (14.86 ± 14.42 ng/ml, p = .027). GH values were not significantly different between non-GHD and ARF-GHD groups. ROC analysis identified a cut-off of serum random GH level of 4.5 ng/ml that achieved 100% sensitivity and 83% specificity for the diagnosis of congenital GHD. CONCLUSION: This study demonstrates that random GH levels obtained in the first 28 days of life can be useful in diagnosing congenital GHD. Moreover, a diagnostic cut-off for congenital GHD using random GH levels was identified.

Method Performance of Bicarbonate and Electrolytes by Use of Duodenal Fluid for Assessment of Exocrine Pancreatic Function.

BACKGROUND: Evaluation of exocrine pancreatic insufficiency is challenging for both clinicians and laboratories. Indirect pancreatic function tests such as serum trypsinogen, fecal elastase, and fecal fat measurements are moderately sensitive for diagnosis of advanced chronic pancreatitis but show reduced sensitivity and specificity for diagnosis of early disease. An alternative is the endoscopic pancreatic function test, which uses duodenal secretions after administration of IV secretin. Samples are collected at various times via the endoscopic tube and then analyzed for bicarbonate, sodium, potassium, and chloride. METHODS: Precision, linearity, method comparison, and stability studies were performed on the Beckman Coulter AU5822 chemistry analyzer with duodenal fluid. Comparison with the Vitros 4600 dry slide chemistry instrument was used to interrogate differences between methods. RESULTS: All assays produced a CV <2% without any measurable effects from the endoscopy fluid matrix and showed acceptable imprecision near the limit of detection (CV < 5%). All analytes showed linear dilution across the analytical measuring range. All the calculated error biases from dilutions were within 50% of the CLIA-allowable error for serum for each of the respective analytes. The calculated slopes ranged from 0.841 to 1.274 when compared to the Vitros 4600. Stability studies demonstrated that sodium, potassium, chloride, and bicarbonate remained stable after storage at -20 °C and after multiple freeze-thaw cycles. The percent change for all analytes was <5% mmol/L. CONCLUSIONS: The AU5800 series demonstrated adequate performance for the analysis of bicarbonate in duodenal fluid and therefore can be used for assessment of exocrine pancreatic function. However, notable discrepancies were observed for sodium, potassium, and chloride between the AU5800 series and the Vitros 4600.

70% Ethanol for Decontamination of Central Venous Lines Exposed to Calcineurin Inhibitors.

BACKGROUND: Tacrolimus, commonly used for graft versus host disease prophylaxis is usually administered via a dedicated central venous line (CVL) and trough levels drawn from the unexposed lumen. Being an oil-based medication, it may be adsorbed to the inner lumen of the CVL and result in falsely high levels drawn from an inadvertently exposed lumen. There is no treatment for decontamination of such CVLs, and natural decay occurs over months before the CVL can be used to draw reliable trough levels. OBJECTIVE: The primary objective of the study was to estimate the effectiveness of 70% ethanol locks for decontaminating CVLs exposed to tacrolimus. METHODS: We studied the efficacy of 70% ethanol lock in decontaminating CVLs exposed to tacrolimus in patients during transplant. Trough tacrolimus levels were drawn from the exposed and unexposed (control) lumens at 8:00 am, followed by a 2-mL 70% ethanol lock instilled for a 2-hour dwell into the exposed (intervention) lumen. Trough tacrolimus levels were again drawn from both lumens at 8:00 pm and levels compared for efficacy. RESULTS: All 20 sets showed a high 8 am trough level in the exposed intervention arm (median = 30 ng/mL), significantly greater ( P < 0.0001) than that in the control arm (median = 9.05 ng/mL), and were contaminated. After the 2-hour ethanol lock, 65% of the lumens were decontaminated. The difference between the control and intervention arms was no longer found to be statistically significant ( P = 0.0826). CONCLUSION: A 2-hour 70% ethanol lock is effective for decontamination of CVLs exposed to tacrolimus.