Evaluating the detection of circulating filarial antigen in diagnosis of bancroftian filariasis and filarial hydrocele.

Four groups of patients were selected: 16 patients with clinical evidence of obstructive filarial lymphangiopathy without microfilaraemia; 12 patients with clinical evidence of obstructive filarial lymphangiopathy with microfilaraemia and 9 patients with microfilaraemia. Two control groups were also included. Blood films, sera and hydrocele fluid samples were collected from all subjects. Polyclonal antibody against Dirofilaria immitis worm homogenate was prepared, fractionated and conjugated with HRP. Both polyclonal antibody and monoclonal antibody (AD12) were used in a sandwich ELISA. Using polyclonal antibody, both microfilaraemic groups (groups 2 and 3) had a significantly higher mean O.D. readings than that of control groups (P < 0.05), whereas, the mean O.D. readings of patients with symptomatic amicrofilaraemia had no significant difference than control groups. Symptomatic microfilaraemic group had the highest percentage of antigen positivity 7/12 (58.3%) among all groups while symptomatic amicrofilaraemic group had the least antigen positivity 2/16 (12.5%). Patients presented with elephantiasis only or with hydrocele had no antigen positive levels 0/12 (0%) in their serum or hydrocele fluid samples. On the other hand, 2 out of 4 cases represented with hydrocele (50%) had positive antigen levels in their hydrocele fluid samples. Using monoclonal antibody, all groups had a highly significant higher mean optical density readings than control groups. Asymptomatic microfilaraemic group had the highest percentage of antigen positivity 8/9 (88.9%), followed by symptomatic microfilaraemic 8/12 (66.7%), then symptomatic amicrofilaraemic group 4/16 (25%). The same 2 patients (amicrofilaraemia) and 7 (microfilaraemia) represented with hydrocele had positive antigen levels in their hydrocele fluid samples.