Diagnosis of Wuchereria bancrofti infection by the polymerase chain reaction employing patients' sputum

A preliminary evaluation of the diagnostic potential of a polymerase chain reaction (PCR) assay using diurnally collected sputum from bancroftian filariasis patients is described. A new set of PCR primers amplifying a 254-bp-long sequence termed AccI, derived from a long dispersed repeated sequence and SspI primers previously employed for PCR-based diagnosis were employed in this study with similar results. Of the 34 sputum samples from patients, 32 (94%) were PCR positive. Of the 18 patients with low to high microfilaremia (21–1560 microfilariae/ml), 16 (88.8%) were PCR positive. Of the remaining 16 patients, 6 with very low microfilaremia (2–6 microfilariae/ml) and 10 without microfilaremia, all (100%) were PCR positive. Two PCR-positive cases among the 13 endemic normal individuals tested (15.4%) may represent cases of occult filariasis. PCR amplification was also demonstrated with one PCR-positive sputum aliquot when mixed with 14 sputum aliquots from uninfected (PCR-negative) individuals. The potential diagnostic merits of the sputum-PCR assay are discussed.