Field validation of sensitivity and specificity of rapid test for detection of Brugia malayi infection

Abstract

SummaryWe 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 ( ‡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.keywords Brugia malayi, rapid test, field validation

Evaluation of Rapid Blood Sample Collection in the Detection of Circulating Filarial Antigens for Epidemiological Survey by rWbSXP-1 Capture Assay

“…This clearly entails that the traditional microscopic method failed to prove its reliability by providing with false negative results. A low density of mf in the system or prepatent infection can lead to CFA in the system but lack mf in the blood smear or any clinical symptoms [24], similar findings were reported with microscopic detections earlier [18], [30], [31]. This cryptic infection which is overlooked during field surveys [32], [33] and control of infection leads to the failure of MDA and eradication of filariasis.…”

Distribution of Brugia malayi larvae and DNA in vector and non-vector mosquitoes: implications for molecular diagnostics

“…Most immunodiagnostic research on filariasis has focused on the parasite stages that occur within the vertebrate host [32,33], and this work has produced sensitive and specific diagnostic tests for Bancroftian and brugian filariasis [5,34,35]. In contrast, few studies have examined antigen detection as a method for identifying and distinguishing LF parasites in mosquitoes.…”

Multicentre evaluations of two new rapid IgG4 tests (WB rapid and panLF rapid) for detection of lymphatic filariasis

“…It has been shown to be highly sensitive (>95%) and specific (≥ 99%) for detection of B. malayi and B. timori infections in laboratory evaluations [ 7 - 10 ] and field studies [ 11 - 14 ]. In a field study in Malaysia which is a low endemic area, Brugia Rapid detected about ten times more positive cases than parasitological diagnosis, while in the high endemic area of Indonesia, the increase in detection was about three times [ 11 , 12 ]. Follow-up post-treatment studies of mirofilaraemic individuals showed that the titres of IgG4 antibodies to Bm R1 decreased post-treatment.…”