| Summary: | INTRODUCTION
High turnover renal osteodystrophy (HTRO) is a highly prevalent complication in patients with chronic kidney disease and mineral bone disease (CKD-MBD), causing pain and significant fracture-associated morbidity and mortality. The diagnostic gold standard test is bone biopsy but there are other, more widely available screening tests such as 1-84 intact parathormone (1-84 iPTH) and nonspecific markers such as total alkaline phosphatase (tALP).
PURPOSE
To determine the diagnostic value (ROC curve, predictive values and likelihood ratios) of 1-84 iPTH and tALP for HTRO screening.
METHODS
A diagnostic accuracy study was performed on a sample of CKD-MDB patients, grouping them according to bone biopsy results and analyzing the results of the diagnostic tests as descriptive variables.
RESULTS
The study group comprised 188 patients with CKD-MDB, 36 of which had biopsy-confirmed HTRO (19.15%). The average age was 50.2 years in the biopsy group, and 53.4 years in the non-biopsy group (p=0.2385), most were male (63.8%) and diabetic (80.5%). The mean time in dialysis was 5.02 years in the biopsy group, and 2.61 years for the non-biopsy group (p<0.001). The mean Kt/V was 1.44 in the biopsy group, and 1.40 in the non-biopsy group (p=0.5354). The mean tALP was 398.02 IU/L in the group with HTRO versus 141.76 IU/L in the group without HTRO (p<0.001). The best cut-off value for tALP was 300-350 IU/L with a near 80% post-test probability, but also with a 15-20% probability for HTRO if the test is negative. The mean 1-84 iPTH was 1248.01 pg/ml in the group with HTRO versus 350.76 pg/ml in the group without HTRO (p<0.001). The 1-84 iPTH cut-off reference value of 300 pg/ml was associated with a post-test probability of 30% for HTRO diagnosis and had a lower overall performance. The best cut-off value for iPTH 1-84 was 600 pg/ml with a post-test probability for HTRO of 70% if positive and less than 5% if the test results are negative.
DISCUSSION
Both markers show good correlation with bone biopsy findings. tALP elevation detects presence of HTRO in selected patients but does not rule it out. tALP does not perform as well as 1-84 iPTH as a screening test for HTRO.
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