dc.description.abstract |
Measles is a severe, vaccine-preventable disease that causes extensive morbidity and
mortality in large parts of the world. Despite the widespread use of measles vaccine,
either as a single antigen vaccine or as a component of the triple vaccine against
measles, mumps and rubella, 278 358 reported cases of measles and an estimated
164 000 deaths from measles occurred worldwide in 2008. Vaccine coverage is
highly variable between World Health Organization global regions. Measles has
been eliminated in the Americas but continues to be endemic in the African and
South-East Asia regions, where vaccine coverage is less than 80%. These regions
account for approximately 94% of all global measles deaths. In Kenya measles and
rubella are still prevalent due to poor vaccination coverage in the neighboring war
tone countries such as Somalia and Southern Sudan. Diagnosis of measles/rubella in
a laboratory set up is usually done by serological examination of particular IgM from
blood sample removed from the veins through puncture. The usual sample collection
method is invasive hence not acceptable. There is need to develop and utilize a noninvasive sample collection technique such as saliva or oral fluid for diagnosis. This
study was aimed at assessing the feasibility of oral fluid as an alternative method for
the detection of measles/rubella-virus specific IgM in routine surveillance of measles
and rubella. The study utilized a prospective laboratory based cross sectional design
using matched serum/oral fluids which were collected during an emerging outbreak
across Kenya of illness characterized by rashes. With a calculated sample size of 180
participants, only 176 participants enrolled and completed the study. Pairs of 176
samples were investigated by enzyme immunosorbent assay for IgM precise
antibodies. The statistical analysis used was kappa (k) statistics to measure interobserver variations. The occurrence of rubella was 26.7% and 23.3% when detected
using serum and oral fluid methods, respectively. When tested against the gold
standard (serum), specificity and sensitivity of rubella IgM in oral fluid was 93% and
86%, respectively. The prevalence of measles among the vaccinated participants was
between 4.2% in Nairobi west, Nakuru North and Wajir East being the least and
Nairobi North 45.8% being the highest. Nairobi north district recorded the highest
percentage (male 33.3% and 66.7% female) because the region is occupied by
refugees from Somalia and Southern Sudan. Rubella virus prevalence among the
vaccinated participants was high compared to negative and indeterminate results
combined. Nairobi North recorded the highest prevalence (64.3%) of rubella for the
two genders while Wajir had the lowest prevalence (3.6%) among the vaccinated
participants in all the Sub-Counties in this study. There was some degree of
agreement between the two methods since the Kappa value was 0.80. On the other
hand, prevalence of measles from oral fluid and serum was 39.8% and 31.8%,
respectively. When tested against the gold standard, specificity and sensitivity of
measles IgM in oral fluid was 97% and 96%, respectively. Kappa statistic value was
0.26 suggesting fair agreement between the two methods. The study concludes that
the use of oral fluid specimen is the best alternative for measles/rubella diagnosis
since it is simple to collect, non-invasive and more acceptable than serum. This
alternative method can be applied in varied clinical set up and is more applicable to
disease surveillance programs. The merit of oral fluids as a specimen for diagnosis is
easy and safe to collect. It is also easily shipped to the laboratory. The results and
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findings of this study strongly suggest the use of saliva in conducting disease
surveillance and epidemiological surveys and studies in Kenya. |
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