[Interference in endotoxin and fungal polysaccharide assays from blood products and antimicrobial agents]

A conventional chromogenic limulus test (CCLT, normal plasma value: less than 10 pg/ml) detects both of endotoxin and beta-1,3-glucan, while a chromogenic endotoxin-specific test (EST: less than 3 pg/ml) detects only endotoxin. Two sources of pseudo-positive result in CCLT and/or EST were studied; (1) factor G-activating material found in blood products, which is indicative of fungal infections, and (2) interaction in diazo-coupling process of the tests by antibiotics or sulfonamides. CCLT and EST values obtained from 13 vials of blood products including human albumin, antithrombin III, and antihemophilic globulin were 284.6 +/- 284.6 pg/ml and 20.2 +/- 26.4 pg/ml (mean +/- SD), respectively. High CCLT values accompanied by low EST values indicate factor G-activating material in the blood products rather than endotoxin. Sample blanks of 42 plasma specimens obtained from 19 patients were 23.7 +/- 34.7 pg/ml by CCLT and 19.2 +/- 31.5 pg/ml by EST. All the patients were administered Sulfamethoxazole/Trimethoprim (SMX/TMP), Aztreonam (AZT), Ceftazidime (CAZ), Imipenem/Cilastatin (IPM/CS), or Silver sulfadiazine. SMX/TMP, AZT, CAZ, IPM/CS, and Cefmenoxime were demonstrated to react with the diazo-coupling reagents used in CCLT and EST, and to cause false-positive result in the tests. Thus the investigation of blood product and sample blank is required for the assay of endotoxins or fungal polysaccharides using CCLT and EST.