Validity of clinical symptoms and chest radiography in predicting pulmonary tuberculosis at the Kenyatta National Hospital, Nairobi, Kenya
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Date
2008Author
Odhiambo, Francesca A
Type
ThesisLanguage
enMetadata
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Background:
Tuberculosis (T8) incidence increases annually by 1% globally, and was
declareda global emergency by the World Health Organization (WHO) in 1993.
Diagnosis of TB infection is confirmed by microscopy of sputum smears for acid fast
bacilli (AFB) while suspicion of the infection is frequently based on clinical
and radiological findings. However, sensitivity of the microscopic diagnosis in
identifying all cases of TB is only 40-60%, and patients with negative sputum
smears for AFB represent a diagnostic dilemma.
Therefore, the gold standard approach for TB diagnosis is to culture the
organism from sputum or blood in a laboratory. Unfortunately this requires
dedicated equipment and takes up to 8 weeks to yield results. It was, therefore,
necessary to develop clinical and chest radiological algorithms that can be
predictors for positive culture in Kenya.
Objective: To establish predictive value of clinical symptoms and chest
radiography in the diagnosis of pulmonary tuberculosis.
Study Design: Prospective cross- sectional survey
Setting: Accident and Emergency department and general medical wards,
Kenyatta National Hospital (KNH), Nairobi Kenya.
Study population: All patients seen in accident and emergency department, and
admitted in the KNH medical wards within the study period with cough for more
than two weeks.
Methodology:
Patients with cough for more than two weeks were screened and those who met
the inclusion criteria were recruited into the study. Each patient was offered HIV
testing after counseling. Three sputa were taken of which one was early morning
sputum for examination for AFB. In addition, confirmatory sputum culture for
Mycobacterium tuberculosis complex was conducted on all patients and the
patients informed about the results by their primary clinician. Chest radiographs
was performed on all recruited patients at the time of recruitment. Two trained
and experienced radiologists blinded to the laboratory diagnosis of TB,
independently assessed the chest radiographs.
Results: A total of 271 were included into the study. Of these 126(46.5%) had
culture proven TB. 55(44%) were HIV positive, 56(44%) were HIV negative and
15(12%) declined to be tested. Sputum smear microscopy had an overall
sensitivity of 71% and specificity of 96%. Smear microscopy was frequently
positive in patients without HIV infection 46(82%) compared to 33(60%) who
were infected with HIV (p=0.019).
Majority 68(54%) of patients with culture confirmed TB were males. The mean
age was 32 years, range 15 to 63 years. The most prevalent symptoms in
patients with TB were weight loss (52%), pleuritic chest pain (45%) and night
sweats (40%). A combination of these three symptoms had 1.3 fold associations
with culture proven infection. On univariate analysis, weight loss (p<0.001),
pleuritic chest pain (p=0.001), night sweats (p<0.001), nodular alveolar infiltrates
affecting upper zones (p<0.001) and cavitations affecting upper zones (p<0.001)
were significantly associated with diagnosis of pulmonary tuberculosis. On
multivariate analysis, weight loss (p=0.001), night sweats (p=0.001), chest pain
(p=0.001), nodular infiltrates affecting upper zones (p<0.001) and cavitations
(p=0.001) independently predicted diagnosis of pulmonary tuberculosis.
HIV positive patients with unintentional weight loss defined as 10% presumed or
measured weight loss in the last one month, were six times more likely to have
T8 (95% CI, 2.73 to 14.5) while haemoptys is was significantly associated with
HIV negative patients (p::;0.009). Likewise HIV positive patients were less likely to
have cavitations (p=0.003) and more likely to have intrathoracic adenopathy
(p=0.043), miliary pattern (p<0.001), diffuse infiltrates (p=0.013) and normal
chest radiographs (0.048) compared to HIV negative patients. HIV positive
patients with positive sputum cultures were less likely to have had a positive
sputum smear compared to HIV negative patients (p=0.019).
Citation
Master of Medicine in Internal Medicine, The University Of Nairobi, 2008.Publisher
University of Nairobi. Faculty of Medicine