A Subgroup of Latently Mycobacterium tuberculosis Infected Individuals Is Characterized by Consistently Elevated IgA Responses to Several Mycobacterial Antigens

Table 2

Specificities and sensitivities of single seroantigens to distinguish between healthy non-TB infected controls [HC ( = 14)] and either active TB patients ( = 42) or LTBI [with medium or high IgA levels ( = 19)].

Antigen	Ig class	TB versus HC		LTBI (elevated IgA) versus HC
		Sens. (%) (95% CI) based on 92.9% (95% CI, 66.1–99.8%) spec.	Sens. (%) (95% CI) based on 100% (95% CI, 76.8–100%) spec.	Sens. (%) (95% CI) based on 92.9% (95% CI, 66.1–99.8%) spec.	Sens. (%) (95% CI) based on 100% (95% CI, 76.8–100%) spec.
NarL	A	81.0 (65.9–91.4)^***	78.6 (63.2–89.7)^***	84.2 (60.4–96.6)^***	84.2 (60.4–96.6)^***
MPT83	A	47.6 (32.0–63.6)^##	2.4 (0.06–12.6)^##	63.2 (38.4–83.7)^###	0 (0.0–17.6)^###
19 kDa	A	64.3 (48.0–78.4)^***	64.3 (48.0–78.4)^***	78.9 (54.4–93.9)^***	78.9 (54.4–93.9)^***
PstS3	A	61.9 (45.6–76.4)^***	35.7 (21.6–52.0)^***	57.9 (33.5–79.7)^***	31.6 (12.6–56.6)^***
AlaDH	G	42.9 (27.7–59.0)^*	28.6 (15.7–44.6)^*	26.3 (9.1–51.2) n. s.	15.8 (3.4–39.6) n. s.
AlaDH	A	76.2 (60.5–87.9)^***	69.0 (52.9–82.4)^***	89.5 (66.9–98.7)^***	84.2 (60.4–96.6)^***

Significance levels of values: values refer to the -test (if appropriate on log-transformed data) or the Mann-Whitney test where indicated. A value of ≤0.05 was judged significant and levels of significance were indicated as follows: ^* or ^# = 0.01–0.05, ^** or ^## = 0.001–0.01, ^*** or ^### < 0.001; asterisks refer to parametric tests, hashes to nonparametric tests.
vs. = versus; n. s. = not significant; sens. = sensitivity; spec. = specificity.
The mean ranks of the IgA signals against the 5 investigated antigens were used to group the LTBI group into the top 19 groups [LTBI with elevated mean IgA levels ( = 19)] and the remaining LTBI group [LTBI (low IgA)].
The data were analyzed by using specificity levels of ≥90%, as described by other investigators [36, 37].