|ESTIMATION OF NUMBER OF REPEAT EXAMINATIONS REQUIRED
TO DETECT ALL TB CASES IN THE COMMUNITY
|R Rajalakshmi & SS Nair: Indian J Public Health
1976, 20, 118-21.
Examination of only one sputum sample cannot detect
all the sputum positive cases in the community. To obtain better
estimates of the prevalence of bacteriologically confirmed disease
in the community, a study was conducted to find out the additional
yield of cases through collection and examination of eight sputum
specimens and also in order to work out correction factors for
estimates based on one or two sputum samples, as collecting multiple
sputa is very difficult. The study was carried out in 77 villages
in Nelamangala Taluk of Bangalore. In all, 5826 persons were referred
for sputum examinations.
Results of all the eight culture examinations were
available for 2973 (51% of the eligibles). Of these 64 persons were
positive by culture of atleast one specimen. Each of the eight specimens
has the chance of detecting a case and any one of them could be
considered as first or second specimen etc. To overcome this difficulty
80 permutations were randomly chosen out of the total 40,320 permutations
possible. Cases from first specimen and additional cases from subsequent
specimens were calculated through four mathematical equations. The
first equation namely Y = KXm (28.66 x-1.40) has been considered
as providing the best fit to the observed data. On the basis of
this equation it appears that additional positives could be obtained
upto the 1Oth specimen. Out of 64 culture positive cases, only 72%
of positives could be detected by first two samples. To get about
95% of the cases, it is necessary to examine at least six specimens
from each individual. Multiple samples are rewarding for detecting
even high grade cultures.
|KEY WORDS: MULTIPLE SPUTUM SPECIMEN, SPUTUM
EXAMINATION, CASE YIELD, PREVALENCE, CASE, SURVEY.