Evaluation of Serum Agglutination and Rose Bengal Tests against Immunofluorescence Antibody Assay in Diagnosis of Brucellosis in Narok and Kiambu County, Kenya
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Date
2015
Authors
Nyagah, Susan, Nyawira
Journal Title
Journal ISSN
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Publisher
Kenyatta University
Abstract
Brucellosis in human is characterized by non specific signs and often misdiagnosed as malaria,
typhoid, rheumatic fever and pyrexia of unknown origin. Definitive diagnosis of brucellosis
requires isolation of Brucella '\PP.but chances of successful isolation decrease as the disease
progresses. In Kenya, the current routine diagnostic test, Serum Agglutination Test (SAT) has a
major drawback in that its not suitable for patient follow-up, since titers can remain high for a
prolonged period. The alternative test, Rose Bengal Test (RBT) is not reproducible as it is very
sensitive to vaccinal antibody limiting its use in vaccinated animals. Immunotlourescence antibody
assay (IF A) has been described as the gold standard for diagnosis ofbrucellosis, To date there is no
study in Kenya that has examined performance of the two ronrme tests STand RBT in the face of
IFA The objective of this study was to evaluate SAT and RBT against IFA and to estimate the
prevalence of brucellosis in Kiambu and Narok counties by the three diagnostic methods. Human
blood and unpasteurised milk samples were collected between December 2009 and August2010 in
Kiambu and Narok counties. A total of 250 human serum and 250 milk samples were collected
from arok and Kiambu counties. Human serum sample was obtained from Kijabe referral
hospital and other neighbouring health facilities. Antibodies to Brucella spp. were screened using
SAT and RBTin the hospital and later transported to Kabete Veterinary Laboratory for IFA Milk
samples were collected from milk vendors packed in cool boxes and transported to Kabete
Veterinary Laboratory where screening was done using one step bovine Brucella antibody rapid
test. All samples were subjected to IFA to determine the prevalence of brucellosis. The overall
prevalence ofbnlcella antibodies by IFAas a gold standard was 3.2% and 70.4% and 14.4% and
54.4% in human samples and milk samples in Kiambu and Narok respectively. Prevalence by SAT
was 10.4% and 77.6% and 8.3% and 80% by RBT in Kiambu and Narok respectively. Comparison
of SAT and IFA gave PPV (63%), NPV (16.4%), sensitivity (75%) and specificity (74%).
Comparison of RBT and IFA gave sensitivity (69.56%), specificity (72.78%), PPV(59.81 %) and
NPV(19.58%). Comparison of One step bovine brucella rapid agglutination test and IFA gave
sensitivity (16.5%), specificity (53.0%), PPV (19.76%) and NPV (52.43%). Prevalence was higher
in females (68%) than males (32%) in Narok particulary 21-30 years. Both SAT and RBT should
be scrapped as they lack sensitivity and specificity. IFA which is accurate, sensitive, specific, rapid
should be recommended as the diagnostic test of choice. People handling animals and their
products are at higher risk of infection.
Description
Department of Medical Laboratory Sciences, 96p. 2015