Sensitivity of the nested-polymerase chain reaction (PCR) assay for Brugiamalayi and significance of 'free' DNA in PCR-based assays

The blood filtration method was used as the gold standard to determine the detection level of simple blood-spot sampling and nested-polymerase chain r eaction (PCR) for Brugia malayi. Of 100 samples, 48 were filtration-positiv e. Of these, 26 had microfilaria counts that were low enough (<1-29 microfi lariae/ml) to accurately assess the limit of detection by nested-PCR. Neste d-PCR consistently detected B. malayi DNA in samples with <greater than or equal to>10 microfilariae/ml, Post-filtration, microfilaria-depleted. blood -spots from microfilaria-positive samples were screened by nested-PCR and B . malayi specific 'free' DNA was detected in 51.7% of these samples. There was no evidence for 'free' DNA in microfilaria-negative individuals from th is endemic community. (C) 2000 Published by Elsevier Science Ltd. on behalf of the Australian Society for Parasitology.