---

Background and objectives: Microscopic agglutination test is the gold standard sero-diagnostic method for detection of leptospirosis. Moreover, it helps identify serovars and their titers in serum samples. For obtaining accurate titer results, proper sampling, collection, storage, and transportation of samples are crucial while maintaining the cold chain. Since storage for long periods and the subsequent deterioration of samples may affect the final titers, we proposed an alternative method of MAT testing using filter paper-dried serum samples. We also evaluated sensitivity and specificity of the MAT test by using filtered-dried serum samples compared with the conventional MAT test.
Methods: This experimental study was performed on human and animal serum samples that were sent to a reference leprospirosis laboratory in 2020. Overall, 142 positive samples (with 289 titers for different strains) and 15 negative samples were used for MAT test using filtered-dried serum. For this purpose, each sample was dried on a filter paper (Whatman 903, GE Healthcare) at room temperature (20-30 °C) and kept for four days. On the fifth day, the filter papers were cut into small pieces, soaked in phosphate buffer saline, vortexed, and slowly mixed on shaker for two hours to elute antibodies. The MAT tests were performed simultaneously and under the same environmental conditions.
Results: The new MAT test using dried serum samples showed 79% sensitivity and 100% specificity. The test also had positive predictive value of 92% and negative predictive value of 24% when compared with the gold standard MAT test.
Conclusion: Filter-dried serum can be used for MAT test to overcome serum storage and transportation problems.

---

Background: Syphilis has serious consequences for human health and poses challenges for biological diagnosis. Techniques such as chemiluminescence are still poorly known in our context. Our objective was to compare chemiluminescence and hemagglutination assays with immunoblot as a reference test for detecting anti-Treponema pallidum antibodies.
Methods: Anti-Treponema pallidum antibodies were detected in serum samples. Comparison of chemiluminescence and hemagglutination assays was carried out with immunoblot as the reference test, based on sensitivity, specificity, positive and negative predictive values, and kappa statistic, using IBM-SPSS version 24 software. The significance level was set at 5%.
Results: A total of 600 participants were recruited, with a prevalence of syphilis infection of 3%. Sensitivity and specificity were 100% and 96.2% for chemiluminescence, and 93.8% and 100% for hemagglutination, respectively. Cohen's kappa statistic between the two tests showed satisfactory agreement (0.768). Cohen's kappa agreements between chemiluminescence/immunoblot and plate hemagglutination assay/immunoblot were greater than 0.8, indicating excellent agreement with the reference test (p<0.0001).
Conclusion: Chemiluminescence is more sensitive but less specific than hemagglutination. The use of chemiluminescence as a first-line test for the diagnosis of syphilis should be considered.