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11 Feb, 2019
Simple & Rapid Point of Care Syphilis Diagnostic Tests
There is a tremendous load of congenital syphilis and syphilis in adults including pregnant women. According to CDC, there is a 43.66 percent increase in congenital syphilis cases in 2017 as compared to 2016.There is around 80% chance of a mother transmitting syphilis to the fetus if not detected or treated. This can lead to stillbirths, prematurity or adverse neonatal outcomes.
Largely in resource poor countries antenatal detection of this old and known enemy (syphilis) is either missed or untreated as the diagnostic tests for syphilis involved sample storage, equipment, reagents , transportation and trained lab personnel. Add to this the time taken to get the reports as also the patient compliance for the second visit to collect reports. Many cases were getting lost in this ordeal. Rapid point of care tests for syphilis are not less than a boon. There are now more than 20 commercially available test kits. Based on the manufacturer, there can be some differences but mainly these are very simple bedside/OPD finger prick tests employing the technique of immunochromatography. So a patient's blood or serum or plasma is fed into the test well and if a coloured line develops on the T (test) site and C (control) site, test is considered positive. The total time till interpretation is around 15 to 20 minutes depending upon the different manufacturing requirements. The sensitivity is around 85-98% and specificity is 93- 98%. These treponemal tests detect antibodies with no prozone effect. But these tests cannot distinguish between active and past treated infections as antibodies to treponemal antigens are retained for years. If the rapid test is positive and RPR (rapid plasma reagin test which is a non-treponemal test) is available, then RPR can be done. Now if RPR is also positive treatment can be started. On the other hand if negative, to be repeated after 6 weeks and if positive treatment to be started. Point to be noted here is if RPR is unavailable and rapid test is positive, treatment should be started.
These rapid point of care diagnostic kits should be always checked for expiry. Hopefully these tests will reduce the undetected burden of syphilis.
Source: WHO
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