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.


METHODS
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 > or =80% in those aged <10 years to <10% in those aged > or =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.


CONCLUSIONS
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.
Nokes
D J
DJ
Department of Biological Sciences, University of Warwick, Coventry, UK. jk@dna.bio.warwick.ac.uk
Nigatu
W
W
Abebe
A
A
Messele
T
T
Dejene
A
A
Enquselassie
F
F
Vyse
A
A
Brown
D
D
Cutts
F T
FT
D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000914:Antibodies, Viral / Q000097:blood* / Q000302:isolation & purification; D002648:Child; D002675:Child, Preschool; D004797:Enzyme-Linked Immunosorbent Assay; D005002:Ethiopia / Q000453:epidemiology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008875:Middle Aged; D011237:Predictive Value of Tests; D015995:Prevalence; D012409:Rubella / Q000453:epidemiology / Q000276:immunology*; D012463:Saliva / Q000821:virology*; D012680:Sensitivity and Specificity; D016036:Seroepidemiologic Studies; D014505:Urban Population
D000914:Antibodies, Viral