Procollagen type I N-terminal propeptide (PINP) is one of the most clinically useful bone formation biomarkers. Therefore, the purpose of this study was to independently evaluate the performance of automated total PINP assay and established age- and gender-specific reference intervals for PINP in healthy Korean population.
The imprecision, linearity, and detection capability of Elecsys total PINP assay was determined and reference interval was established using 599 serums from Korean population with normal bone mineral densities based on bone densitometry. Age groups were divided into 20s, 30s, 40s, 50s, 60s and over.
Elecsys total PINP had excellent performance in imprecision, linearity, and detection capability. When partitioning age groups in Korean male and female populations, there was significant difference in total PINP between different age groups. In male populations, PINP level was decreased with increasing age, then it remained steady after middle-age. In female populations, there was a decreasing tendency similar to that in the male population with a sharp increase in the 50 to 59 age group.
Elecsys total PINP assay showed precise and reliable performance in our study. We established age-related PINP reference intervals for Korean male and female population with normal bone mineral densities.
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The purpose of this study was to find out the cause of discrepancy between various automated immunoassays for 25-hydroxy-vitamin D (25-[OH]D).
National Institute of Standards & Technology Standard Reference Material (SRM) 972a is SRM for 25-(OH)D and consists of 4 vials of frozen serum with different concentrations of 25-(OH)D. Each concentration was measured 6 times in 3 different immunoassays: ADVIA Vitamin D Total assay (Siemens Healthcare, Erlangen, Germany), ARCHITECT 25-(OH)D (Abbott Laboratories, Abbott Park, IL, USA), and COBAS Vitamin D Total assay (Roche Diagnostics, Basel, Switzerland).
When using the certified reference values of SRM 972a as it is, discarding the cross-reactivity of each immunoassay, for ADVIA, the coefficient of determination (R2) as a score of regression analysis was 0.8995 and maximal difference between measured value and certified reference value was 3.6 ng/mL in level 3. The R2 and maximal differences of ARCHITECT were 0.5377 and 6.9 ng/mL, respectively, in level 4. Those of COBAS were 0.3674 and 22.3 ng/mL, respectively, in level 4. When considering cross-reactivities of each immunoassays to various 25-(OH)D metabolites, the ADVIA had R2 and maximal difference of 0.9254 and 3.3 ng/mL, respectively, in level 3. For ARCHITECT, the R2 and maximal differences were 0.7602 and 5.1 ng/mL, respectively, in level 1. Those of COBAS were 0.9284 and 4.9 ng/mL, respectively, in level 1.
The cause of discrepancies between vitamin D immunoassays was mainly on the difference in cross-reactivities to various vitamin D metabolites. The discrepancies can be considerably decreased by considering cross-reactivities of each immunoassay.
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