Clinical evaluation of the plasma chromogenic Limulus assay

Clinical correlations of the plasma chromogenic Limulus assay were evaluated in 520 septic episodes to assess the diagnostic utility of the assay in a university hospital setting. Otherwise unselected patients undergoing blood culture were studied. An association of plasma Limulus activity with gram negative bacteremia and focal infections was found (p less than .001 and p less than .01, respectively). There was a lesser correlation between a positive assay and the presence of major hepato-intestinal illness (p = .05). The frequency of positive tests was similar for adult and pediatric groups. There were modest correlations of a positive assay with hypotension (p = .02) and thrombocytopenia (p = .04), but only among patients with gram negative infection. Abnormal neutrophil parameters were unassociated with positive assays in any group. The sensitivity and specificity of the test for a condition known to cause endotoxemia--either gram negative infection or major intestinal disease--were low, 21% and 93% respectively. However, the predictive value of a positive test was 79%, indicating utility for the assay.