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 calculate the measurement uncertainty of the process of bone mineral density (BMD) analysis using dual energy X-ray absorptiometry with traceability.
Between March 2015 and October 2016, among healthy participants in their 20s and 30s, the study included those who had not taken calcium, vitamin D supplements and steroids and were without a history of osteoporosis, osteopenia and diseases related to osteoporosis. Relational expression of the model was established based on Guide to the Expression of Uncertainty in Measurements and Eurachem and the uncertainty from each factor was evaluated.
The combined standard uncertainty was 0.015, while the expanded uncertainty was 0.0298. The factor-specific standard uncertainties that occurred in the process of measuring BMD were 0.72% for the calibration curve, 0.9% for the internal quality control (IQC) using Aluminum Spine Phantom, 0.58% for European Spine Phantom (ESP), and 0.9% for the inspector precision (IP).
The combined standard uncertainty of the spine BMD corrected with ESP was 0.015 when measured at one time and targeting one participant. The uncertainties of the accuracy of the IQC and the IP were higher than that of the other factors. Therefore, there will be a need for establishment of protocols to lower these uncertainties.
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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Although dual energy X-ray absorptiometry (DXA) is known to standard equipment for bone mineral density (BMD) measurements. Different results of BMD measurement using a number of different types of devices are difficult to use clinical practice. The purpose of this study was to evaluate discrepancy and standardizations of DXA devices from three manufactures using a European Spine Phantom (ESP).
We calculated the accuracy and precision of 36 DXA devices from three manufacturers (10 Hologic, 16 Lunar, and 10 Osteosys) using a ESP (semi-anthropomorphic). The ESP was measured 5 times on each equipment without repositioning. Accuracy was assessed by comparing BMD (g/cm2) values measured on each device with the actual value of the phantom. Precision was assessed by the coefficient of variation (CVsd).
Lunar devices were, on average, 22%, 8.3%, and 5% overestimation for low (L1) BMD values, medium (L2), and high (L3) BMD values. Hologic devices were, on average, 6% overestimation for L1 BMD, and 5% and 6.2% underestimation for L2 and L3 BMD values. Osteosys devices was, on average, 12.7% (0.063 g/cm2), 6.3% (0.062 g/cm2), and 5% (0.075 g/cm2) underestimation for L1, L2, and L3, respectively. The mean CVsd for L1-L3 BMD were 0.01%, 0.78%, and 2.46% for Lunar, Hologic, and Osteosys devices respectively.
The BMD comparison in this study demonstrates that BMD result of three different devices are significant different between three devices. Differences of BMD between three devices are necessary to BMD standardization.
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