TABLE 6.

Independent evaluation of smear versus culture for each processing method^a

Smear value	No. of specimens with smear value
	NALC/NaOH		CB-18
	AFB positive	AFB negative	AFB positive	AFB negative
−	28	506	37	439
±	3	0	5	25d
1+	7	1b	8	14e
2+	8	1c	6	2f
3+	5	0	7	0
4+	14	0	30	0
Total	65	508	93	480

^aIn this analysis, the smear and culture data from NALC/NaOH-processed specimens were considered independent of the results generated from CB-18 processing (e.g., all smear and culture results generated from processing with CB-18 were ignored), and the results were first segregated as either NALC/NaOH culture positive or NALC/NaOH culture negative. The smear results after NALC/NaOH processing were then overlaid on these culture results to categorize the specimen data. The analogous breakdown was then performed with results from processing with CB-18. The smear sensitivities (AFB positive) were 56.9% for NALC/NaOH and 60.2% for CB-18. The smear specificities (AFB negative) were 99.6% for NALC/NaOH and 91.5% for CB-18. 

^bThis specimen was from a patient previously culture positive for MAC and Nocardia sp. This specimen was also culture positive for MAC when processed by the CB-18 method. 

^cThis specimen was from a patient previously positive for MTBC. In addition, this specimen was also 2+ smear positive when processed by the CB-18 method. 

^dOne of these specimens was culture positive for M. gastri, and two of these specimens were culture positive for MTBC when processed with NALC/NaOH. 

^eOne of these specimens was culture positive for MTBC when processed with NALC/NaOH. 

^fOne of these specimens was from a patient previously positive for MTBC. The same specimen was also 2+ smear positive and culture negative when processed with NALC/NaOH.