High yield of culture-based diagnosis in a TB-endemic setting

BMC Infectious Diseases

Table 3 Smear and culture results for all SE, smear negative and smear positive SE

Description	All smears	All cultures	Cultures in SN SE	Cultures in SP SE
Number of SE	2537	2537	2060	477
Observed # of P SE after 1 specimen	377	682	253	429
Observed # of P SE after 2 specimens	477	733	301	432
Proportion of P SE on 1^st specimen	0.149	0.269	0.123	0.899
Proportion of NP SE	0.060	0.042	0.040	0.103
# of P SE missed by failing to do 2^nd specimen	31	27	25	2
Expected # of P SE after 1 specimen	377	682	253	429
Expected # of P SE after 2 specimens	508	760	326	434
Expected proportion of P SE after 1 specimen	0.149	0.269	0.123	0.899
Expected proportion of P SE after 2 specimens	0.200	0.299	0.158	0.910
Potential IY for 1^st specimen	0.743	0.898	0.776	0.989
Potential IY for 2^nd specimen	0.257	0.102	0.224	0.011
Overall fraction of P on 1^st specimen	0.149	0.269	0.123	0.899
Overall fraction of P on 2^nd specimen	0.052	0.031	0.035	0.010
NND on 1^st specimen	7	4	8	1
NND on 2^nd specimen	19	33	28	96

Legend: S = smear, P = positive, N = negative, SE = Suspect Episodes, NND = number needed to diagnose (see Methods for details), IY = incremental yield.

ISSN: 1471-2334