Determinação de valores próprios de referência para vitamina D, hormônio paratireoideo e cálcio em um laboratório de análises clínicas

Abstract

AIMS: To determine the proper reference intervals for vitamin D, parathyroid hormone (PTH) and calcium in a clinical laboratory.METHODS: A retrospective cross-sectional study was carried out at the units of Alfa Ltda. Laboratory, located in Caxias do Sul, in the mountain region of Rio Grande do Sul. The sample included self-declared healthy clients and laboratory workers. The study was based on two research methods (direct and indirect) proposed by the Clinical & Laboratory Standards Institute for the establishment of proper reference intervals for a specific laboratory. The direct method (DM) involved questionnaire application, collection and analysis of blood samples and the indirect method (IM) consisted of database analysis.RESULTS: Results of 241 individuals were evaluated in the DM, of which 120 were female. The mean age of participants was 33.8±10.6 years. IM resulted in 5,485 values for vitamin D, 191 for PTH, and 856 for calcium. The mean age of the individuals was 45.0±15.6 years, 49.0±15.3 years and 48.87±15.41 years, respectively. The proper reference intervals obtained by the DM were statistically equal to those of the IM for the three dosages. When comparing the reference intervals obtained with those available in the manufacturer report, vitamin D resulted in a lower range of normality (report: >30 ng/mL; MD: 10-47 ng/mL; MI: 11-46 ng/mL), PTH in a higher range (report: 15-68.3 ng/mL; MD: 19.2-81.6 ng/mL; MI: 26.1-94.3 ng/mL), and calcium presented very close values (report: 8.3-10.6 ng/mL; MD: 8.3-10.2 ng/mL; MI: 8.2-10.1 ng/mL). There was a statistical difference between the reference intervals established for vitamin D and calcium between genders.CONCLUSIONS: Both MD and MI were efficient for the determination of proper reference intervals. The reference intervals established in the study, specifically for vitamin D and PTH, were different from those suggested in the manufacturer's package insert, which reinforces the recommendation of establishing proper reference intervals for each laboratory.