The COV for each of the laboratory ELISAs was calculated based on the Student t-distribution of the negative control sera readings, following

the equation by Dixon and Massey, 1983 [16, 17]. The equation used for the COV calculation is as follows: (1) The antifilarial IgG4-ELISA was performed as above with a few modifications, using sera from brugian filariasis patients. BmR1 filarial recombinant antigen (20 μg/mL) was used to coat the microtitre plate. The secondary antibody, antihuman IgG4-HRP, was diluted to 1 : 4500. Serial dilutions of the serum samples were made from 1 : 200 to 1 : 25 600 in PBS, pH 7·2. The Strongyloides find more Serology Microwell ELISA (IVD Research, Inc., Carlsbad, CA, USA), which is based on the detection of human IgG antibodies against Strongyloides spp. antigen, was performed according to the manufacturer’s instructions. In brief, serum samples were diluted 1 : 64 in dilution buffer and incubated for 10 min in the antigen-coated wells. After three washes with wash buffer, two drops of conjugate solution were added and incubated for 5 min. Subsequently, Tanespimycin nmr the wells were washed again as described above followed by the addition of two drops of chromogenic solution. Following a 5-min incubation, the reaction was stopped with two drops of stop solution,

and the results were immediately read at 450 nm (reference: 620 nm). The COV given for this test is 0·200. The statistical significance of the difference in S. stercoralis-specific antibody titres was analysed by one-way

anova test. Pearson correlation coefficient (r) test was used to analyse the correlations among the levels of IgG and IgG4, IgG and IgG (IVD) and IgG4 and IgG (IVD) antibodies to Strongyloides spp. Spearman correlation test was used to analyse correlation between the anti-Strongyloides IgG4 (OD405) results and the antifilarial IgG4 antibody titres in filariasis serum. Statistical tests were performed using GraphPad Prism version 5 (San Diego, CA, USA). In addition, a paired t-test was used to determine whether the difference in the specificities of the two IgG-ELISAs was significant. In all cases, differences 17-DMAG (Alvespimycin) HCl were considered as statistically significant when P < 0·05. In this study, we examined parasite-specific IgG4, IgG and IgE responses against S. stercoralis infection using laboratory ELISAs as well as a commercial IgG-ELISA (IVD). The COVs and results obtained for all ELISAs are shown in Table 2. Of the 26 patients who were faecally positive for Strongyloides, 20 were seropositive for specific IgG4 antibody with a sensitivity rate of 76·9%, 22 (84·6%) were seropositive by both laboratory and commercial (IVD) IgG tests, and only 2 were seropositive for parasite-specific IgE antibody (7·7%). Further studies using much larger sample size will need to be performed to confirm the results of this small scale study. These preliminary findings would be a useful guide in designing the larger study.