Evaluation of Gamma Interferon and Antibody Tuberculosis Tests in Alpacas | Clinical and Vaccine Immunology

DOI: 10.1128/CVI.00405-12

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Table 1

Observed IFN-γ test sensitivity and specificity values

Test result^{^a}	VL alpacas (n = 55)			TB-free alpacas (n = 257)
Test result^{^a}	n/55	% sensitivity	95% CI	n/257	% specificity	95% CI
PPD⁺	35	63.6	50.9–76.3	28	89.1	85.3–92.9
EC⁺	27	49.1	35.9–62.3	26	89.9	86.2–93.6
EC⁺ PPD⁻	8	14.5	5.2–23.8	21	91.8	88.4–95.2
PPD⁺ EC⁺	19	34.6	22.0–47.2	5	98.1	96.4–99.8
PPD⁺ or EC⁺	44	80.0	69.4–90.6	49	80.9	76.1–85.7

↵a PPD, PPDB − PPDA; EC, ESAT6-CFP10 peptide cocktail.

Table 2

Increasing the IFN-γ test specificity values

Test result^{^a}	VL alpacas (n = 55)			TB-free alpacas (n = 257)
Test result^{^a}	n/55	% sensitivity	95% CI	n/257	% specificity	95% CI
PPD⁺	16	29.1	17.1–41.1	8	96.9	94.8–99.0
EC⁺	16	29.1	17.1–41.1	8	96.9	94.8–99.0
EC⁺ PPD⁻	7	12.7	3.9–21.5	8	96.9	94.8–99.0
PPD⁺ EC⁺	9	16.4	6.6–26.1	0	100.0	98.6–100
PPD⁺ or EC⁺	23	41.8	28.8–54.8	16	93.8	90.9–96.7

↵a PPD, PPDB − PPDA; EC, ESAT6-CFP10 peptide cocktail.

Table 3

Antibody test sensitivity and specificity values

Test	VL alpacas			TB-free alpacas
Test	n/total	% sensitivity	95% CI	n/total	% specificity	95% CI
Stat-Pak	35/52	67.3	54.5–80.8	8/306	97.4	95.6–99.2
DPP	30/52	57.7	44.3–71.1	10/306	96.7	94.1–98.4
Idexx	36/52	69.2	56.7–81.7	8/306	97.4	95.6–99.2
Enferplex	32/48	66.7	53.4–80.0	8/257	96.9	94.8–99.0

Table 4

IFN-γ and antibody test combinations and sensitivity and specificity values^{^a}

Test combination	VL alpacas (n = 48)			TB-free alpacas (n = 257)
Test combination	n/48	% sensitivity	95% CI	n/257	% specificity	95% CI
IFN-γ + Stat-Pak	45	93.8	87.0–100	52	79.2	74.2–84.2
IFN-γ + Idexx	44	91.7	83.9–99.5	55	78.6	73.6–83.6
IFN-γ + DPP	44	91.7	83.9–99.5	58	77.4	72.3–82.5
IFN-γ + Enferplex	45	93.8	87–100	58	77.4	72.3–82.5
IFN-γ + Stat-Pak + Idexx	48	100	92.6–100	57	77.8	72.7–82.9
IFN-γ + Stat-Pak + DPP	48	100	92.6–100	60	76.7	71.5–81.9
IFN-γ + Stat-Pak + Enferplex	47	97.9	93.8–100	60	76.7	71.5–81.9
IFN-γ + Idexx + DPP	45	93.8	87.0–100	62	75.9	70.0–81.2
IFN-γ + Idexx + Enferplex	44	91.7	83.9–99.5	62	75.9	70.0–81.2
IFN-γ + Enferplex + DPP	47	97.9	93.8–100	65	74.7	69.4–80

↵a IFN-γ positive, PPDB-PPDA > 0.1 or EC-nil > 0.1.

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