Screening for tuberculosis among 2381 household contacts of sputum-smear-positive cases in The Gambia.
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 smear-positive 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 1518/100000. 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 >or=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.
Jackson-Sillah
Dolly
D
Bacterial Diseases Programme, MRC Laboratories, Box 273, Banjul, The Gambia.
Hill
Philip C
PC
Fox
Annette
A
Brookes
Roger H
RH
Donkor
Simon A
SA
Lugos
Moses D
MD
Howie
Stephen R C
SR
Fielding
Katherine R
KR
Jallow
Adama
A
Lienhardt
Christian
C
Corrah
Tumani
T
Adegbola
Richard A
RA
McAdam
Keith P
KP
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D016358:Contact Tracing / Q000379:methods*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods / Q000592:standards; D005191:Family Characteristics; D005260:Female; D005714:Gambia / Q000453:epidemiology; D006801:Humans; D007223:Infant; D008297:Male; D008403:Mass Screening / Q000379:methods; D008875:Middle Aged; D015995:Prevalence; D012680:Sensitivity and Specificity; D012882:Skin Tests / Q000379:methods; D013183:Sputum / Q000382:microbiology; D014374:Tuberculin Test; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis / Q000453:epidemiology*