Usefulness of an in-vitro tuberculosis interferon-γ release assay (T-SPOT.TB) in the first-line check-up of uveitis patients

Figures & data

Table I. Definitions for TST positivity, chest imaging classification, and suspected intraocular tuberculosis.

TST	Negative	The diameter of the skin induration was < 10 mm in BCG-vaccinated or < 5 mm in non-vaccinated patients
	Positive	The diameter of the skin induration was ≥ 10 mm in BCG-vaccinated or ≥ 5 mm in non-vaccinated patients
Chest imaging	Abnormal	Paratracheal and/or mediastinal lymphadenopathy
	Suggestive of present or past tuberculosis	Cavitations, calcified lymphadenopathies, micronodules, miliary nodule aspect, tree-in-bud appearance (11,12)
Suspected intraocular tuberculosis	A patient with a positive TST and/or pulmonary abnormalities on chest CT scan, and no other cause of uveitis
Presumed intraocular tuberculosis	A patient with suspected intraocular tuberculosis and reduction of inflammation and recurrences after specific antituberculosis treatment, for a minimum of 6 months' follow-up (mean 18.9 ± 8.1 months) after antibiotic treatment withdrawal (6,33)

TST = tuberculin skin test.

Table II. Epidemiological, clinical and paraclinical investigations for the 108 uveitis patients according to their TST and T-SPOT^®.TB status.

	All patients	TST		T-SPOT.TB
Test result		−	+	−	+
	n = 108	(n = 48, 44.4%)	(n = 60, 55.6%)	(n = 76, 70.4%)	(n = 32, 29.6%)
Age: mean ± SD (years)	49.4 ± 19.1	48.5 ± 20.04	50 ± 18.41	45.8 ± 18.51	57.67 ± 18.06;(P = 0.003)
Male/female ratio	0.8	0.5	1.22;(P = 0.025)	0.72	1.13
Previous contact with a tuberculous patient	32 (29.6)	9 (18.8)	23 (38.3);(P = 0.027)	18 (23.7)	14 (43.8);(P = 0.03)
BCG vaccination	92 (85.2)	43 (89.6)	49 (81.7)	70 (92.1)	22 (68.8);(P = 0.003)
Chest imaging Normal	71 (65.7)	33 (68.8)	38 (63.3)	55 (72.4)	16 (50)
Abnormal	31 (28.7)	13 (27.1)	18 (30)	18 (23.7)	13 (40.6)
Suggestive of tuberculosis	6 (5.6)	2 (4.2)	4 (6.7)	3 (3.9)	3 (9.4);(P = 0.07)

P = statistical significance of differences between group of positivity and negativity for each test (P values were not noted when P > 0.1); SD = standard deviation.

Figure 1. Patient with proved tuberculosis. A: Photograph of the fundus showing retinal hemorrhages and occlusive vasculitis of the left eye. B: Fluorescein angiography of the left eye showing vasculitis, with absence of dye filling in some retinal arteries masking retinal hemorrhages. C: Tuberculous cavitation on CT scan. D: Highly positive T-SPOT^®.TB test (panel A, ESAT-6 = 177 spots).

Figure 2. Patient with presumed intraocular tuberculosis and serpiginous choroiditis. A: Fundus photography showing white dots at the choroid, in the posterior pole of the left eye. B: Fluorescein angiography showing hyperfluorescence at the rim of the lesions and hypofluorescence in the center of the lesions. C: Indocyanine angiography showing hypofluorescence of the lesions. D: Highly positive T-SPOT^®.TB test (panel B, CFP-10 = 57 spots).

Table III. Epidemiological, clinical, and paraclinical investigations for the 108 uveitis patients included in the study according to their classification as uveitis with determined or undetermined cause, and suspected ocular tuberculosis cases.

Group	Uveitis with determined etiology (n = 38)	Uveitis with undetermined etiology (n = 52)	Suspected ocular tuberculosis cases (n = 18)	P-value
Age (years)	47.1 ± 18.8	48.9 ± 18.8	55.2 ± 20.3	0.3
Male/female ratio	1.11	0.67	0.8	0.5
Previous contact with a tuberculous patient	8 (21.1)	13 (25)	11 (61.1)	0.005
BCG vaccination	34 (89.5)	44 (84.6)	14 (77.8)	0.5
TST positive	16 (42.1)	26 (50)	18 (100)	<0.001
T-SPOT^®.TB test positive	5 (13.2)	10 (19.2)	17 (94.4)	<0.001
TST+/T-SPOT.TB+	4 (10.5)	7 (13.5)	17 (94.4)	<0.001
TST+/T-SPOT.TB−	12 (31.6)	19 (36.5)	1 (5.6)
TST−/T-SPOT.TB+	1 (2.6)	3 (5.8)	0
TST−/T-SPOT.TB−	21 (55.3)	23 (44.2)	0
Chest imaging
Normal (%)	24 (63.2)	40 (76.9)	7 (38.9)	0.02
Abnormal (%)	12 (31.6)	11 (21.2)	8 (44.4)
Abnormal, suggestive of tuberculosis (%)	2 (1.9)	1 (0.9)	3 (2.8)
Types of ocular lesions
Anterior	5 (13.2)	16 (30.8)	0	0.08
Intermediate	2 (5.3)	3 (5.8)	1 (5.6)
Posterior	3 (7.9)	6 (11.5)	5 (27.8)
Panuveitis	13 (34.2)	14 (26.9)	6 (33.3)
Choroiditis	10 (26.3)	10 (19.2)	5 (27.8)
Vasculitis	5 (13.2)	3 (5.8)	1 (5.6)

Table IV. Test performance of TST, T-SPOT^®.TB in the population of 108 uveitis patients (95% confidence interval are noted in brackets).

n = 108	Sensitivity	Specificity	PPV	NPV	Accuracy	LR+	LR−
TST	100%	53.3%	30% (70%)	100% (0%)	61.1%	2.14	0
	(81.5–100)	(42.5–63.9)	(18.8–43.2)	(92.6–100)	(51.2–70.3)
T-SPOT.TB test	94.4%	83.3%	53.1% (46.7%)	98.7% (1.3%)	85.2%	5.67	0.07
	(72.7–99.9)	(74.0–90.4)	(34.7–70.9)	(92.9–99.9)	(77.1–91.3)
TST and T-SPOT.TB	94.4%	87.8%	60.7% (39.3%)	98.8% (1.3%)	88.9%	7.73	0.06
test positive	(72.7–99.9)	(79.2–93.7)	(40.6–78.5)	(93.2–99.9)	(81.4–94.1)
TST or T-SPOT.TB	100%	48.9%	28.1% (71.9%)	100% (0%)	57.4%	1.96	0
test positive	(81.5–100)	(38.2–59.7)	(17.6–40.8)	(92.0–100)	(47.5–66.9)

PPV and NPV = positive and negative predictive values; LR+ and LR− = positive and negative likelihood ratios; TST = tuberculin skin test.

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