The LDH ratio as a marker for response to plasma exchange in HUS/TTP of the adult. Haas M, Leko-Mohr Z, Lang T, Jansen M, Knobl P, Horl WH, Druml W. Clinical Nephrology 2002;57(6):414-420.

ABSTRACT:

Plasma exchange (PE) improved the outcome of hemolytic uremic syndrome/ thrombotic thrombocytopenic purpura (HUS/TTP) of the adult markedly, but a high number of non-responders remain. Identifying these patients at an early stage would help to optimize therapy. This study determined the value of serologic measures in predicting the response to PE. The authors performed a retrospective chart review of 30 adult patients with HUS/TTP treated with PE. According to the treatment protocol, a mean of 42 +/- 8.2 ml plasma per kilogram of body weight was exchanged daily for 3 days and continued every second day thereafter. Prior to each session, clinical status and serologic markers for hemolysis and kidney function were obtained. To assess the early individual response to PE, the decline of lactic dehydrogenase (LDH) from the first to the third cycle was calculated as: LDH concentration before the third session/LDH concentration before the first session (LDH ratio). During the observation period (median 195, range 6-1500 days), 80% of the patients responded to therapy with plasmapheresis. None of the serologic measures or clinical signs obtained before initiation of PE showed a significant correlation with the outcome. After two sessions of PE, only LDH and platelet level had improved markedly in responding patients. The LDH ratio was the best predictive marker for the individual response. An LDH ratio less than 0.6 predicted a favorable outcome with a sensitivity of 0.96 and a specificity of 0.83. The LDH ratio might be a useful marker for separating patients responding to plasma exchange from those not responding at an early stage.