Table 3.
Yield and percentage of interferon gamma release assay-positive results obtained by implementing latent tuberculosis infection screening at different tuberculosis incidence thresholds.
| Threshold: TB incidence in country-of-birth | Number screened (%) | Number IGRA positive | Yield (% IGRA positive of those tested) | Percent of all IGRA positives correctly identified | |
| >350/100 000 | 66 | (6.3) | 9 | 13.6% | 7.6% |
| >250/100 000 | 129 | (12.3) | 20 | 15.5% | 16.9% |
| >150/100 000 | 556 | (52.8) | 94 | 16.9% | 79.7% |
| >150/100 000 plus all sub-Saharan African countries: the proposed ‘PWH-LTBI streamlined guidance’ | 568 | (53.9) | 106 | 18.7% | 89.8% |
| >50/100 000 | 614 | (58.3) | 106 | 17.3% | 89.8% |
| ≥40/100 000 plus risk factors: BHIVA 2018 guidelinesa[14] | 622b | (59.1) | 110 | 17.7% | 93.2% |
| Screen all PWH:∗ 2016 NICE guidelines [13], ECDC guidelines for the EU/EEA [11], WHO guidelines for low tuberculosis burden countries [12] | 1053 | (100) | 118 | 11.2% | 100% |
BHIVA, British HIV Association; ECDC, European Centre for Disease Prevention and Control; EEA, European Economic Area; EU, European Union; IGRA, interferon gamma release assay; NICE, National Institute for Health and Care Excellence. All included guidelines mention dual use of IGRA/Mantoux testing in some, or all PWH. We have assumed in this table that IGRA is as effective at diagnosing LTBI as Mantoux.
Recommends screening all those from high (≥150/100 000 population) or medium (40–150/100 000 population) TB incidence countries; only screening those from low-TB-burden countries (<40/100 000 population) if additional risk factors for TB are present: CD4+ cell count less than 200 cells/μl; recent exposure to a known TB case; diabetes mellitus; stage 4/5 chronic kidney disease; receipt of chemotherapy for malignancy; immunosuppression following transplantation; biological disease modifiers for inflammatory conditions; prolonged duration of high-dose corticosteroids (prednisolone 20 mg o.d., or equivalent, for ≥2 months); travel to or periods of time spent in medium-incidence or high-incidence countries; history of working in medical settings in countries with medium or high TB incidence; injecting drug use (detailed in Table 6.1 of guidance [14]).
This figure is an underestimate (includes all patients from countries where TB at least 40/100 000 population; plus four IGRA-positive patients from countries where TB incidence less than 40/100 000 for whom BHIVA cited additional risk factors were evident, but does not include patients with negative IGRA results from countries where TB incidence less than 40 of 100 000 because BHIVA-cited risk factors were not collected prospectively.