Letter on the relation between serum Ca, PO4, and PTH with mortality in dialysis patients

Abstract

In the CHOICE dialysis cohort, Melamed et al. 1 found in their lagged analysis that intact PTH levels o76 pg/ml were associated with a 35% lower mortality compared to levels of 160-308 pg/ml. In order to appropriately discuss this observation in relation with National Kidney Foundation-Kidney Disease Outcomes Quality Initiative optimal intact parathyroid hormone (PTH) of 150-300 pg/ml, we think that these figures have to be first corrected by the 50% lower median bias induced by the Diasorin intact PTH assay when compared with the Nicholls Allegro assay to which Kidney Disease Outcomes Quality Initiative is referring. 2 This means that Allegro PTH o150 pg/ml would be associated with a better survival than PTH of 300-620 pg/ml. This certainly challenges the National Kidney Foundation-Kidney Disease Outcomes Quality Initiative recommendation 3 of preventing a PTH o150 pg/ml. This is not too surprising as this recommendation was just based on claims of a few authors (cited by Melamed) who pointed out a link between low bone turnover and mortality. Furthermore, this recommendation disregarded the results of the bone histomorphometric study meta-analysis suggesting that Allegro PTH o60 pg/ml best predicted low bone turnover. It should be, however, noted that the observation by Melamed et al. is in agreement with the most recent prognostic evaluation of PTH by Block et al., 4 which, owing to better adjustment with other comorbidities (specially malnutrition), did not find anymore a higher mortality with Allegro PTH o150 pg/ml, but found a higher mortality when PTH was 4600 pg/ml.

Interaction between parathyroid hormone and the Charlson comorbidity index on survival of incident haemodialysis patients

“…PTH has been often associated with higher mortality rate [17][18][19][20]. Instead, survival analyses have yielded conflicting results on the effects of low PTH [17][18][19][20][21][22][23].…”