A comparison of oral fluid and serum for the detection of rubella-specific antibodies in a community study in Addis Ababa, Ethiopia
objective To assess the utility of oral fluid compared with serum for the determination of age-prevalence of rubella-specific antibodies in an urban African community setting.
method Paired serum and oral fluid samples were collected from 439 individuals aged 0–49 years in Addis Ababa, Ethiopia, as part of a larger seroepidemiological survey in 1994. Oral fluid was sampled using a simple sponge device that was well accepted by subjects of all ages; venous blood was collected by Vacutainer system. We measured rubella-specific antibodies in serum by the Radial Haemolysis (RH) test, supported by two confirmatory assays, and in oral fluid by IgG antibody-capture radioimmunoassay (GACRIA).
results Sensitivity and specificity of oral fluid results compared to serum were 89% and 76%, respectively. Sensitivity declined from 96% in age group 0–19 years to 90% in age group 20–29 and 78% in age group 30–49. Specificity was 86% in 0–9 year olds contrasting with 61% in older groups (10–49 years). The positive predictive value of an oral fluid sample was high in all age groups (range 92–100%), while the negative predictive value declined from ≥80% in those aged <10 years to <10% in those aged ≥30 years. Serum confirmatory tests suggested a proportion of false serum RH negatives, increasing with age, indicating a need to standardize serum as well as oral fluid tests.
conclusion In the community setting of a developing country, oral fluid surveys could be useful to estimate age-prevalence of rubella immunity and identify rubella-susceptible children for follow-up. Further work is required to simplify assays and sample processing, improve assay sensitivity and estimate assay specificity more precisely, and compare and standardise collection methods suitable for surveillance of a variety of childhood viral infections.
Document Type: Research Article
Affiliations: 1: Department of Biological Sciences, University of Warwick, Coventry, UK, 2: Ethiopian Health and Nutrition Research Institute, Addis Ababa, Ethiopia, 3: Department of Community Health, Faculty of Medicine, University of Addis Ababa, Ethiopia, 4: Virus Reference Division, Central Public Health Laboratory, London, UK, 5: Infectious Disease Epidemiology Unit, London School of Hygiene and Tropical Medicine, UK
Publication date: 01 April 1998