Assessing feasibility of using Oral Fluid assay as Alternative method in the Detection of Rubella Virus-Specific IgM Antibodies in routine disease surveillance Programme in Kenya

Abstract

Background: The WHO recommends the inclusion of rubella testing in the measles surveillance system. Laboratory diagnosis of measles and rubella virus infection is achieved by serological assay for specific IgM from a sample of blood drawn by vein puncture. This conventional method of sample collection is invasive and less acceptable.

Aim: To assess feasibility of using oral fluid as an alternative method in the detection of rubella-virus specific IgM in routine surveillance of rubella

Settings and Design: A prospective laboratory-based cross-sectional study using matched oral fluid and serum collected from emerging outbreaks of rash-like illnesses across Kenya.

Methods and Material: Matching samples of 176 patients were investigated for IgM specific antibodies using enzyme linked immunosorbent assays.

Statistical analysis used: The kappa (k) statistic was used to measure inter-observer variations.

Results: The prevalence of rubella using serum and oral methods was 26.7% and 23.3% respectively. Sensitivity and specificity for rubella IgM in oral fluid when tested against the gold standard was 86% and 93% respectively.  Kappa statistic value was 0.80 suggesting substantial agreement between the two methods.

Conclusion: The study showed that oral fluid method is a promising simple alternative, non-invasive and more acceptable specimen of choice for rubella diagnosis. The alternative method will be more applicable to disease surveillance programmes where clinical settings are varied. The advantage of this method of sample collection is ease and safety with minimum requirement for shipment to laboratory. These findings will support the entire disease surveillance system in Kenya and also can have extended use in conducting epidemiological studies.

Key words: Oral fluid, serum, diagnosis, surveillance, prevalence, diseases, measles and rubella