Intact parathyroid hormone: comparison of the 2nd generation Abbott (Architect, Alinity) and Roche (Cobas) assays in relation to the management of patients with chronic kidney disease on dialysis

The letter focuses on the issues of insufficient standardization of methods for determination of intact parathyroid hormone (iPTH) level. The use of the recommended diagnostic thresholds of iPTH expressed as a ratio to the upper reference limit for the method does not provide sufficient harmonization of the results. This is possibly explained by the variability of the reference groups used by the manufacturer to develop the reference limits specified in the instructions for reagents. When using iPTH 2nd generation assays manufactured by Roche and Abbott for a parallel study of a series of the same samples, despite the similarity of upper reference limit values specified in the instructions (Roche Cobas e601: 15-65 pg/ml; Abbott Architect i2000 and/or Alinity i: 15-68.3 pg/ml), whose ratio is close to 1 (1,048), more significant differences were revealed. The ratio of the results in measuring the concentration of iPTH in pg/ml using Abbott Alinity i (y) and Roche Cobas 601e (x) technologies in the same sample series (n=70, including 40 samples of dialysis patients) is described by the regression equation y = 1.255x + 3.79. Using Abbott Alinity technology in a reference group of practically healthy individuals with no vitamin D deficiency we developed the reference limits for intact PTH, which were 1.3-9.7 ng/ml (12.3-91.5 pg/ml). According to the reference limits developed in own conditions, the clinically significant thresholds of 1x, 2x, 4x, 9x from the upper reference limit for Abbott (Architect, Alinity) iPTH technologies in concentration units are approximately 90-180-350-800 pg/ml.

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