Age partitioned and continuous upper reference limits for Ortho VITROS High Sensitivity Troponin I in a healthy paediatric cohort.

OBJECTIVES: In adults, the elevation of cardiac troponin (cTn) above the 99th percentile upper reference limit defines myocardial injury. The use and interpretation of cTn in a paediatric population, however, is difficult given the 99th percentile for different assays is not well established. Using paediatric blood samples from healthy neonates, infants and children we derived continuous and partitioned 97.5th and 99th percentiles for the Ortho VITROS hs-TnI assay. METHODS: A total of 328 samples for infants, children and adolescents aged 0-17.8 years were obtained. Age partitioned reference limits were derived in accordance with CLSI EP28-A3C. Continuous reference limits were established as described previously by the HAPPI Kids Study team. RESULTS: hs-TnI as measured by the Ortho VITROS Assay is highly elevated above the adult 99th percentile at birth and declines to lower levels within the first 6 months of life. The 99th centile upper reference limit for ages 0-3 months was 72 ng/L (90% CI: 52-91) and 9 ng/L (90% CI: 5.2-17.4) for ages 3 months to 18 years. Continuous upper 99th centile reference limits were comparable. CONCLUSIONS: Partitioned and continuous 99th percentiles for hs-TnI were derived for the new Ortho VITROS assay in healthy neonates and older children. This will assist clinicians to appropriately assess for the presence of myocardial injury in this population.

Sweat testing for cystic fibrosis: standards of performance in Australasia.

BACKGROUND: Accurate measurement of sweat chloride concentration is essential for the diagnosis of cystic fibrosis (CF). We surveyed all laboratories enrolled in the Royal College of Pathologists of Australasia Quality Assurance Program (QAP) for Sweat Electrolytes to determine how closely they comply with the Australian Guidelines for the performance of the sweat test for the diagnosis of CF. METHODS: A detailed questionnaire covering most aspects of sweat collection and analysis was sent to all participating laboratories in 2007. RESULTS: Twenty out of 38 laboratories completed the questionnaire. While adherence to accepted guidelines was noted in many areas, the following main variations were recorded: some laboratories were not doing enough sweat tests to maintain expertise; some were not collecting sweat for the recommended collection time; sweat conductivity was the only test available in some laboratories; there was a lack of agreement between the sweat chloride concentration used to indicate CF or define an equivocal result. CONCLUSIONS: There is room for improvement in the performance of the sweat test in some laboratories in Australasia. The Sweat Testing Working Party of the Australasian Association of Clinical Biochemists is the appropriate body to address the problems involved in sweat testing and to bring about change.

Luteinizing hormone and follicle-stimulating hormone levels in extreme prematurity: development of reference intervals.

OBJECTIVES: Establishing pediatric reference intervals has always been challenging, with most ranges used in pediatric laboratories developed over many years. The clinical interpretation of gonadotropins is important in the context of ambiguous genitalia. The aim of this study was to develop reference intervals for luteinizing hormone and follicle-stimulating hormone in infants born between 24 and 29 weeks' gestation. METHODS: Samples were collected at 0 to 43 days after birth from 82 premature infants born <30 weeks' gestation for analysis of luteinizing hormone and follicle-stimulating hormone by automated immunochemiluminometric immunoassays. RESULTS: The 43 male infants demonstrated a range of luteinizing hormone levels from 0.1 to 13.4 IU/L and of follicle-stimulating hormone levels from 0.3 to 4.6 IU/L. The 39 female infants demonstrated a range of luteinizing hormone levels from 0.2 to 54.4 IU/L and of follicle-stimulating hormone levels from 1.2 to 167.0 IU/L. The ratio of luteinizing hormone/follicle-stimulating hormone levels differed with males, ranging from 0.3 to 9.4, and females, at <0.5. CONCLUSION: These data provide guidance for the interpretation of luteinizing hormone and follicle-stimulating hormone levels for the first 6 weeks of life in extremely premature infants born between 24 and 29 weeks' gestation. The availability of age-appropriate reference intervals is essential for correct and timely interpretation of biochemical results to the clinician.