**2. Materials and Methods**

### *2.1. Setting and Clinical Procedures*

The study protocol was approved by the Ethics Committee of the Reggio Emilia Province on 19 April 2017 and by the Reggio Emilia Local Health Unit on 5 June 2017 (document code 2017/DS/0038).

This study took place in the CFF of Reggio Emilia, an area in northern Italy with approximately 550,000 inhabitants. The CFF is an outpatient clinic located in the city centre. It is devoted to immigrants without a valid residence permit, who are not entitled to choose a general practitioner.

In accordance with national recommendations [10], the reference test for the diagnosis of LTBI is the tuberculin skin test (TST) based on the Mantoux method. TST is carried out by the nursing staff in accordance with the Mantoux method, by inoculating 0.1 mL of purified protein [11]. The nursing or medical staff read the induration in millimetres after 48–72 h. If positive, the TST is always evaluated by medical personnel. The cut-off for TST positivity is usually 10 mm. In case of immunosuppression, it drops to 5 mm. Screening is performed according to a local protocol based on the combined use of TST and interferon gamma release assay (IGRA). Specifically we have used Quantiferon-TB Gold (QFT) for evaluating the possible presence of active TB. In Figure 1 it is possible to see the algorithm used at CFF for the screening of active TB and LTBI; in immigrants with any symptom of TB and/or peripheral lymphadenopathy, TST is performed as a first step. As far as TB symptoms are concerned, we consider at least one of the following: cough, haemoptysis, fever, chest pain, weight loss, fatigue, night sweats, chills or loss of appetite. The clinician visiting the patient may prescribe CXR at the time of TST and at any time during the screening protocol if a high risk for active TB is estimated. If the CXR shows any abnormality, the patient is referred for the pneumological examination (PE) or hospitalization. If CXR is negative, the patient's LBTI diagnosis can be proceeded with. TST-positive patients undergo CXR (if not ye<sup>t</sup> performed) and possibly QFT. QFT is generally prescribed for confirmation for the purpose of offering LTBI treatment. The indication for LTBI treatment is decided by the pneumologist, after patient examination and evaluation of CXR and QFT results. For LTBI treatment, we generally prescribe isoniazid for 6 months at a dose of 5 mg/kg/day, combined with vitamin B6, in order to prevent neurological adverse effects. Isoniazid preventive therapy (IPT) is recommended in people

aged ≤35 years and in people of any age with HIV co-infection. In case of contraindication, failure to accept or need to discontinue IPT, patients with LTBI undergo health surveillance (HS) through clinical examination every six months for two years, for the purpose of early detection of the onset of active TB symptoms.

**Figure 1.** Procedures for active tuberculosis (**TB**) and latent tuberculosis infection (**LTBI**) screening at the Centre for Health of Foreign Family (**CFF**) of Reggio Emilia. **TST**: Tuberculin Skin Test; **CXR:** chest X-ray; **PE:** Pneumological Examination; **POS:** positive; **NEG:** negative.

All examinations and visits are free of charge. Cultural mediators belonging to the most common ethnic groups of patients are constantly present to assist health personnel and immigrants during outpatient activity.

### *2.2. Study Design and Definitions*

In this retrospective cohort study, all foreign-born patients aged ≥15 years who underwent TST at the CFF between 1 January 2012 and 31 December 2013 were enrolled, provided that there was no evidence of previous contact with a case of pulmonary TB or positive TST. The period of active follow-up in patients undergoing HS ended on 31 December 2016. We defined patients with LTBI as immigrants with both positive TST and QFT and patients with positive TST but QFT not requested or not performed. We considered patients without LTBI as subjects with negative TST and with positive TST but negative QFT. According to the World Health Organization [12], a bacteriologically confirmed TB case was one from whom a biological specimen was positive by smear microscopy, culture or rapid diagnostic tests (such as Xpert MTB/RIF assay that is a nucleic acid amplification test). A clinically diagnosed TB case was one diagnosed with active TB by a clinician or other medical practitioner who decided to start a full course of TB treatment; this definition included cases diagnosed on the basis of X-ray abnormalities or suggestive histology and extra pulmonary cases without laboratory confirmation.
