Diagnostic Accuracy of Serum Parathyroid Hormone Levels in Kidney Transplant Recipients with Moderate-to-Advanced CKD

Abstract

Background/Aims: Elevated parathyroid hormone (PTH) is used to diagnose high turnover bone disease in chronic kidney disease (CKD). The diagnostic accuracy of PTH in kidney transplant recipients with CKD is unknown. Methods: We examined kidney transplant recipients with CKD stages 3 (n = 498) and 4 (n = 141) to determine the sensitivity and specificity of the Kidney/Dialysis Outcome Quality Initiative (K/DOQI)-recommended PTH levels in detecting elevated serum β-CrossLaps (CTX) or osteocalcin (OC) levels. We performed receiver-operator curve analyses to determine CKD stage-specific PTH levels that provide optimal diagnostic accuracy. Results: PTH below the lower limits of the K/DOQI ranges (35 and 70 pg/ml in CKD stages 3 and 4, respectively) showed sensitivity of >90% in diagnosing increases in biochemical markers. The upper limits (70 and 110 pg/ml), however, showed poor specificity. A specificity of >90% for detecting increased biochemical markers was seen with PTH of >140 and >240 pg/ml in CKD stages 3 and 4, respectively. Conclusion: Currently applied cutoffs for PTH in kidney transplant recipients with CKD stages 3 and 4 do not appear to adequately detect increased biochemical markers of bone turnover. Diagnostic uncertainty exists in patients with CKD stage 3 and PTH between 35 and 140 pg/ml, and CKD stage 4 and PTH between 70 and 240 pg/ml.