Table 3.

Correlation between smear result category and positive culture result

	Conventional Microscopy		Fluorescence Microscopy
Smear Result*	Total	Culture-positive (N, %)	Total	Culture-positive (N, %)	p-value†
Negative	485	131 (27%)	446	124 (28%)	0.58
Scanty (1–9 AFB/100 fields)	48	43 (90%)	67	36 (54%)	<0.001
1+ (10–99 AFB/100 fields)	70	64 (91%)	57	47 (82%)	0.02
2+ (1–10 AFB/field)	41	40 (98%)	45	43 (96%)	0.62
3+ (> 10 AFB/field)	72	72 (100%)	101	100 (99%)	N/A††

Abbreviations: AFB, acid-fast bacilli

^*To compare conventional and fluorescence microscopy on the same scale, the number of AFB observed with fluorescence microscopy was divided by a correction factor of 10 to adjust for the lower level of magnification. The actual number of AFB observed with fluorescence microscopy was: Negative, 0 AFB/length; Scanty, 1–99 AFB/length; 1+, 100–999 AFB/length; 2+, 10–100 AFB/field; and 3+, > 100 AFB/field.

^†Compares proportion of positive cultures within each smear result category for conventional and fluorescence microscopy.

^††3+ smear result category dropped from the model due to co-linearity.