Influence of four different PTH methods on the classification of chronic kidney disease patients according to the new KDIGO guideline.

BACKGROUND

Secondary hyperparathyroidism develops frequently with chronic kidney disease (CKD) and is associated with poor outcome. The new CKD-MBD guideline, Kidney Disease: Improving Global Outcomes (KDIGO), recommends a target range for PTH which is based on the locally used, upper reference range limit (URL). We examined the impact of the KDIGO guideline on the classification of dialysis patients in two different hospitals using 4 different intact-PTH assays.

METHODS

Blood samples from 76 consecutive hemodialysis CKD patients were measured for PTH concentration. Classification of the patients was performed according to the previous KDOQI and the KDIGO guideline using the manufacturers' and laboratory determined URLs. Classification of patients based on 3 different PTH methods (Siemens ADVIA Centaur, Siemens Immulite 2000, and Beckman Coulter Unicel DxI) was compared with the classification found in another hospital using the Roche Modular E170 PTH assay.

RESULTS

Depending on the PTH assay used, between 9 (12%) to 14 (18%) of the patients were classified differently in the two hospitals if the KDOQI guideline was followed. Application of the KDIGO-PTH target range resulted in a similar or decreased number of differently classified patients if the PTH concentration was measured using the Advia Centaur and Immulite assays. With the Beckman Coulter PTH assay, however, the number of differently KDIGO-classified patients increased if the manufacturers' URL (9.3 pmol/L) was used to calculate the PTH-target range. Application of the laboratory determined URL (7.0 pmol/L) improved concordance in classification, although the number of differently classified patients was still higher than with the other PTH assays. The best concordance in classification for the Beckman Coulter assay was found at a PTH value of 6.0 pmol/L. Regarding the Roche and Siemens assays, no significant difference was found in the classification using the URL either determined by the laboratory or the manufacturers.

CONCLUSIONS

Compared with the KDOQI guideline, the new KDIGO guideline may increase the number of discrepancies in the classification of CKD patients if the Access Beckman Coulter PTH assay is used in conjunction with the calculated target range based on the manufacturers' URL. The best concordance in the classification for the Beckman Coulter assay was found at a PTH value below the manufacturers' and laboratory determined URL.