Prevalence of latent tuberculosis infection among multinational healthcare workers in Muhayil Saudi Arabia

Objectives: The aim of this work was to assess the prevalence of latent tuberculosis infection (LTBI) in multinational healthcare workers (HCWs) in Muhayil, Saudi Arabia. Materials and methods: This work was carried out in 2013 and included all hired HCWs in Muhayil National Hospital (MNH), Muhayil, south of Saudi Arabia. Data were collected from HCWs including age, sex, job category, and country of citizenship. They were examined for LTBI using the tuberculin skin test (TST) after obtaining their consent to perform the test. CXR was also carried out in all participants to (and if needed sputum stain for Mycobacterium tuberculosis smear) for the detection of active disease. Statistical analysis was carried out, and P values less than 0.05 were considered significant. Results: Out of the 208 HCWs tested with TST, 47 (22.5%) were positive. The prevalence of LTBI was the highest in the age group of 50 years or more [26.3% (n = 5)] and the lowest in the age group 20-29 years [19% (n = 14)]. The prevalence of LTBI was the highest in nurses [28.7% (n = 21)] and the lowest in physicians [16.5% (n = 7)]. The prevalence of LTBI was the highest in HCWs from the Philippines [27.5% (n = 23)] and the lowest in HCWs from the Middle East, Saudi Arabia, and Yemen [16.5% (n = 3)]. Signs suggestive of inactive TB were found in 10% of the participants (N = 21), and all of them were TST positive (44.5% of all TST-positive participants). Conclusion: LTBI is prevalent in HCWs in MNH, especially in nurses and in HCWs from countries with high rates of tuberculosis (Philippine and South Asia).


Introduction and aim of the work
According to the WHO, one-third of the world's population is already infected with TB and every second, someone somewhere is newly infected with tuberculosis [1].
Tuberculosis can be considered both a nosocomial and an occupational infection [2]. TB in healthcare workers (HCWs) is often caused by an infection at their workplace [3]. Adequate infection control measures by the hospital authorities, high suspicion of tuberculosis by clinicians, and early identifi cation of latent tuberculosis infection (LTBI) are necessary to prevent tuberculosis among HCWs [4]. Tuberculin skin test (TST) testing is an accepted inexpensive method for the detection of LTBI despite debates on its limitations and eff ectiveness in individuals recently vaccinated with BCG [5].
Most published data on LTBI in HCWs in Saudi Arabia were from hospitals of big cities such as Riyadh and Jeddah, and not much data are available for HCWs in remote areas such as Muhayil South of Saudi Arabia.
Th e aim of this work was to assess the prevalence of LTBI in HCWs in Muhayil, Saudi Arabia.

Materials and methods
Th is work was carried out in 2013 and included all hired HCWs in Muhayil National Hospital (MNH), Muhayil, south of Saudi Arabia (after obtaining the consent of the participants). Data were collected from each HCW including age, sex, job category, and country of citizenship. Th ey were examined for LTBI using TST by an injection (using a 26-G needle) of 0.1 ml (5 U) of purifi ed protein derivative intracutaneously (Mantoux test) into the volar aspect of the forearm. Th e reaction was read 48-72 h later; the size of the reaction was determined by measurement of the induration, not the erythema. A measurement equal to or more than 10 mm was considered positive [6]. Th e test was performed and read by the chest consultant in MNH. Plain posteroanterior Chest X Ray (CXR) was also performed for all participants (and if needed sputum stain for Mycobacterium tuberculosis smear) for the detection of active disease. Th e X rays were examined by the radiology consultant in Muhayil National Hospital (MNH). Th e study methods were approved by the Muhayil National Hospital ethical committee.
Th e results of the TST testing and CXR were analyzed with other variables.

Statistical analysis
Statistical analysis was carried out using the SPSS program (version 14; SPSS Inc., Chicago, Illinois, USA). Odds ratios (ORs) were calculated. All P values less than 0.05 were considered signifi cant in this study.

Results
Of the 208 participants in this work (Table 1), 36 were physicians (32 from the Middle East and four from Yemen), 73 were nurses (54 from Philippines, 11 from South Asia, three from Middle East and fi ve from Yemen), 29 were technicians (10 from Philippines, nine from South Asia, one from Saudi Arabia and nine from Yemen), 39 were administrators (four from Philippines, four from South Asia, seven from the Middle East, and 23 from Saudi Arabia), and 31 were handy workers (15 from Philippines and 16 from South Asia).
Chest X ray was performed for all participants in this work (N = 208) and signs suggestive of inactive TB were found in 10% (N = 21); all of them were TST positive (44.5% of all TST-positive participants). Th e overall percent of agreement between positive tuberculin and positive CXR was 87.5%, the positive percent agreement was 44.7%, and the negative percent agreement was 100%. None of the participants had CXR fi ndings suggestive of active TB (thus, no sputum smear examination was performed) (Tables 6 and 7).

Discussion
According to the WHO 2014 global TB report [7], there were 9.0 million new TB cases and 1.5 million TB deaths in 2013.
Th e overall prevalence of LTBI (TST positive) in the participating HCWs was 22.5% (47 out of 208), which is higher than that reported by Abbas et al. [8], who found a prevalence of 11% among HCWs in four major tertiary care hospitals in Riyadh, Saudi Arabia, and higher than that that reported by Nienhaus et al. [9], who found a prevalence of 26.7% (TST, Mantoux method). Th e prevalence of LTBI was much higher (79%) among HCWs of King Abdulaziz University Hospital, Saudi Arabia [10]. Other studies showed a higher prevalence of LTBI in HCWs (40.8%, 79%) [11,12].
In this work, the prevalence of LTBI in HCWs was the highest in the age groups 40-49 years (26%) and at least 50 years (26.3%) and was the lowest in the age group 20-29 years (19%). Nienhaus et al. [9] reported that the prevalence of LTBI increased from 4.6% in HCW younger than 30 years to 69.2% in HCW older than 60 years. Other studies reported an increased prevalence of LTBI in HCWs with increased age [8,[13][14][15].
Th e prevalence of LTBI was 22% in men and 23% in women, without a signifi cant diff erence. A similar fi nding (with lower results of 7.2% in men and 7.1% in women) was reported by Schablon et al. [13]. In another study [16], female HCWs had a higher prevalence of LTBI than male HCWs.
Th e higher prevalence of LTBI among nurses than among physicians in this work can be attributed to the diff erences in the burden of TB in their country of citizenship [all participating physicians were from the Middle East and Yemen and most of the participating nurses (65 out of 73) were from South and Southeast Asia (Table 1)]. Kassim et al. [12] studied TST to assess the occupational risk of M. tuberculosis infection among HCWs in Abidjan, Côte D'Ivoire, and reported that out of the 512 participants, 405 (79%) had a TST reaction of at least 10 mm, eight (2%) were anergic, and fi ve (1%) had a radiograph compatible with TB.

Conclusion and recommendation
LTBI is prevalent among HCWs in MNH, especially among nurses and HCWs from countries with high rates of tuberculosis (Philippine, India, Pakistan, and Bangladesh). Because HCWs in Saudi Arabia are from multiple nationalities and mostly from areas with a high prevalence of TB (South and Southeast Asian countries), pre-employment and postemployment assessment of TB must be considered for better control of TB (especially among HCWs).