Gel clot LAL assay in the initial management of peritoneal dialysis patients with peritonitis: a retrospective study

Abstract

Background: Indiscriminate use of broad-spectrum antibiotic treatment of peritonitis in peritoneal dialysis patients may have either unwanted side-effects or contribute to the development of antibiotic resistance. This may be avoided by improved diagnosis at presentation. The Limulus amoebocyte lysate assay is a convenient test detecting bacterial endotoxins or fungal beta glucans. This study evaluates a qualitative Limulus amoebocyte lysate test as a diagnostic tool used at presentation of a peritoneal dialysis patient with peritonitis.

Methods: One-hundred and eleven episodes of peritonitis in peritoneal dialysis patients have been analysed retrospectively. Limulus amoebocyte lysate results at presentation were compared with culture results. A Limulus amoebocyte lysate assay was performed using a commercial kit by incubating a mixture of dialysate effluent and Limulus amoebocyte lysate reagent at 37 degrees C. The development of a stable solid clot was considered positive. The specificity and sensitivity of the test were calculated.

Results: The specificity of the Limulus amoebocyte lysate assay was found to be 98% and the sensitivity 74%. Limulus amoebocyte lysate assay was false-negative in 13 cases of Gram-negative peritonitis (22%). Limulus amoebocyte lysate was positive in three of seven cases of fungal peritonitis. The study included one case each with false-positive Limulus amoebocyte lysate and with culture-negative peritonitis.

Conclusions: The Limulus amoebocyte lysate assay is a convenient and valuable diagnostic tool for excluding Gram-positive peritonitis in peritoneal dialysis patients. This allows more specific antibiotic treatment at presentation and may avoid the development of bacterial resistance. A negative Limulus amoebocyte lysate test is not reliable for the exclusion of Gram-negative peritonitis. In the absence of a positive culture result 48 h after presentation, accompanied by a delayed response to treatment, a positive Limulus amoebocyte lysate assay may indicate the presence of fungus. This justifies early empiric antifungal treatment before definitive culture results are made available. Routine Limulus amoebocyte lysate assay of dialysate effluent from continuous ambulatory peritoneal dialysis patients presenting with peritonitis is recommended.