Dolly Jackson-Sillaha, Philip C. Hill a,∗, Annette Foxa, Roger H. Brookesa,
Simon A. Donkora, Moses D. Lugosa, Stephen R.C. Howiea,
Katherine R. Fielding b, Adama Jallowc, Christian Lienhardtd,
Tumani Corraha, Richard A. Adegbolaa, Keith P. McAdama
Summary Contact investigation is a key component of tuberculosis (TB) control in developed,
but not developing, countries. We aimed to measure the prevalence of TB among household
contacts of sputum-smear-positive TB cases in The Gambia and to assess the sensitivity of an
enzyme-linked immunospot (ELISPOT) assay in this regard. Household contacts of adult smearpositive
TB patients were assessed by questionnaire, purified protein derivative (PPD) skin test,
ELISPOT assay, physical examination, chest X-ray and sputum/gastric aspirate. Thirty-three
TB cases were identified from 2174 of 2381 contacts of 317 adult smear-positive pulmonary
TB patients, giving a prevalence of 1518/100 000. The cases identified tended to have milder
disease than those passively detected. The sensitivity of ESAT-6/CFP-10 ELISPOT test as a
screening test for TB disease was estimated as 71%. Fifty-six per cent of contacts with a PPD
skin test result ≥10mm induration had detectable responses to ESAT-6/CFP-10 by ELISPOT; 11%
with a negative PPD skin test (<10mm) had a positive ESAT-6/CFP-10 response. Active screening
for TB among contacts of TB patients may have a role in TB control in The Gambia. These individuals
are a high-risk group, and the disease identified is less advanced than that found through
passive case detection. An ELISPOT assay was relatively insensitive as a screening test for TB.
© 2007 Royal Society of Tropical Medicine and Hygiene. Published by Elsevier Ltd. All rights
reserved.
Screening for tuberculosis among 2381 household contacts of sputum-smear-positive cases in The Gambia