A total of 753 serum samples from 6 institutions in 3 countries (Malaysia, Indonesia and India) were used to evaluate an immunochromatographic rapid dipstick test, Brugia Rapid, for diagnosis of Brugia malayi infection. The samples comprised sera from 207 microfilaria-positive individuals and 546 individuals from filaria non-endemic areas. The latter consisted of 70 individuals with soil-transmitted helminth infections, 68 with other helminth infections, 238 with protozoan infections, 12 with bacterial and viral infections and 158 healthy individuals. The dipstick is prepared with a goat anti-mouse antibody control line and a B. malayi recombinant-antigen test line. First, the dipstick is dipped into a well containing diluted patient serum, thus allowing specific anti-filarial antibody in the serum to react with the recombinant antigen. Then the dipstick is placed into an adjacent well containing reconstituted anti-human IgG4-gold. After 10 min, development of 2 red-purplish lines denotes a positive result and one line indicates a negative reaction. The overall results of the evaluation showed 97% sensitivity, 99% specificity, 97% positive predictive value and 99% negative predictive value. Brugia Rapid is thus a promising diagnostic tool for detection of B. malayi infection, and would be especially useful for the brugian filariasis elimination programme.
Angiostrongylus cantonensis is the most frequent cause of eosinophilic meningitis in humans in Thailand and worldwide. Because of difficulty of recovering the Angiostrongylus larvae from infected patients, detection of parasite-specific antibodies is used to support clinical diagnosis. This study tested serum samples from eosinophilic meningitis patients and individuals at risk of infection with A. cantonensis to evaluate a recently developed simple and rapid dot-immunogold filtration assay (DIGFA) for detection of specific antibodies against A. cantonensis. Purified 31-kDa glycoprotein of A. cantonensis and protein A colloidal gold conjugate were employed to detect the 31-kDa anti-A. cantonensis antibody in patients sera from the parasite endemic areas of northeast Thailand. The results were compared with those obtained by dot-blot enzyme-linked immunosorbent assay (ELISA) with 31-kDa A. cantonensis antigen. The overall positivity rate of DIGFA and dot-blot ELISA for A. cantonensis infection in 98 clinically diagnosed cases from three highly endemic districts in Khon Kaen province were 39.79% and 37.75%, respectively. Among 86 sera of subjects at risk of infection with A. cantonensis, 24.41% were positive by DIGFA and 23.25% by dot-blot ELISA. There were good correlation between the visual grading of DIGFA and dot-blot ELISA in both groups of defined sera. DIGFA is as sensitive and specific as dot-blot ELISA for confirming eosinophilic meningitis due to A. cantonensis infection, with advantages of simplicity, rapidity and without the use of specific and expensive equipment, and can be used in field settings.
We conducted a field study of a rapid test (Brugia Rapid) for detection of Brugia malayi infection to validate its sensitivity and specificity under operational conditions. Seven districts in the state of Sarawak, Malaysia, which are endemic for brugian filariasis, were used to determine the test sensitivity. Determination of specificity was performed in another state in Malaysia (Bachok, Kelantan) which is non-endemic for filariasis but endemic for soil-transmitted helminths. In Sarawak both the rapid test and thick blood smear preparation were performed in the field. The rapid test was interpreted on site, whereas blood smears were taken to the district health centres for staining and microscopic examination. Sensitivity of Brugia Rapid dipstick as compared with microscopy of thick blood smears was 87% (20/23; 95% CI: 66.4-97.2) whereas the specificity was 100% (512/512). The lower sensitivity of the test in the field than in laboratory evaluations (> or =95%), was probably due to the small number of microfilaraemic individuals, in addition to difficulties in performing the test in remote villages by field personnel. The overall prevalence of brugian filariasis as determined by the dipstick is 9.4% (95% CI: 8.2-0.5) while that determined by microscopy is 0.90% (95% CI: 0.5-1.3) thus the dipstick detected about 10 times more cases than microscopy. Equal percentages of adults and children were found to be positive by the dipstick whereas microscopy showed that the number of infected children was seven times less than infected adults. The rapid dipstick test was useful as a diagnostic tool for mapping and certification phases of the lymphatic filariasis elimination programme in B. malayi-endemic areas.