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Latent tuberculosis infection in healthcare workers at a community hospital in Qatar

Dr. Humberto Guanche Garcell

By Dr. Humberto Guanche Garcell

Dr. Humberto Guanche Garcell MD MPH Hospital Epidemiologist. Hospital ¨Joaquín Albarrán¨. Assistance Professor by the Cuban Medical University and Assistance Researcher by the Cuban Academy of Sciences. La Habana, Cuba

Garcell, H. G., Ramirez, E. C., Contreras, A. K., & Garcia, F. G. (2014). Latent tuberculosis infection in healthcare workers at a community hospital in Qatar. Journal of infection and public health, 7(4), 356-359.

Summary

Routine screening of latent tuberculosis infection (LTBI) is recommended as an essential component in the prevention of TB transmission in healthcare facilities.

Objective: To determine the prevalence of LTBI among healthcare workers (HCWs) in a community hospital.

Methods: A descriptive study was carried out at The Cuban Hospital from August 2012 to May 2013 for newly hired medical staff. As part of the preemployment evaluation, the tuberculin skin test (TST) and QuantiFERON-TB Gold In-Tube test (QFT-G) were performed. The information regarding the demographics, profile, experience as HCWs, any previous contact with TB patients and travels abroad were collected.

Analysis: Test of independence, Student’s t test and Wilcoxon Mann—Whitney were used. For hypothesis testing, a significance level of 0.05 was adopted.

Results: TST results were positive in 14 subjects (6.9%), of which 11 were nurses, and 12 were females. QFT-G results were positive in six subjects (3.0%), who were older than those with negative results (44.5 vs. 38.9 years) and had more experience as HCW (21.7 vs. 16.8 years). Compared with subjects negative for QFT-G, positive subjects reported a higher frequency of both direct contact with tuberculosis patients (83.3% vs. 25%) and previous travels to countries with high TB incidence.

Conclusion: Incidence of LTBI was low, especially when QFT-G results were considered, highlighting the history of traveling to countries with high TB incidence as an associated key factor.

Introduction

As the risk of tuberculosis (TB) infections for healthcare workers (HCWs) is higher than in the general population, routine screening is recom- mended [1,2]. The risk of transmission in healthcare facilities is related to the local prevalence of TB, the characteristics of the patient population and the effectiveness of TB infection control programs [2]. Screening programs using the tuberculin skin test (TST) or the QuantiFERON TB Gold In-Tube test (QFT-G) have identified the incidence of latent tuberculosis infection (LTBI) in different settings in Spain (11.2%), India (50%), Korea (51%) and England (7.6%) [3—6].

According the World Health Organization (WHO) data, in Cuba, the incidence of tuberculosis infec- tion is 6.1 cases per 100 000 habitants [7], which is considered a low incidence rate. In HCWs, two studies have shown LTBI prevalence of 15.4% in a General Hospital and 50% in a hospital dedicated to TB management [8,9]. Other data report LTBI of 26.6%, 28.8% and 31.5% in hospitals of La Habana City (Borroto S. Institute of Tropical Medicine Pedro Kouri, La Habana, 2013, unpublished).

The aim of this study was to assess the prevalence of LTBI among the Cuban medical staff at a community hospital in Qatar.

Methods

A descriptive study was carried out at The Cuban Hospital, a community healthcare facility member of Hamad Medical Corporation, the largest health- care provider in Qatar. According to the national laws and regulations, during the hiring process,  all HCWs should undergo a mandatory medical evaluation to rule out infectious diseases such as tuberculosis, viral hepatitis and others.

Tuberculin skin test (TST) was performed by trained nurses according to the WHO standard Man- toux technique, using 2 tuberculin units (0.1 ml) of purified protein derivates RT 23. The test was read 72 h later using 10-mm diameter as the cut-off point. QuantiFERON-TB Gold In-Tube test (QFT-G) was performed in those with a positive TST test, considering the 0.35 IU/mL concentration of IFN-g (interferon gamma) as the negative/positive cut- off to confirm LTBI. To rule out active tuberculosis, lung X-ray was performed; if needed, sputum for acid-fast bacilli identification was also performed. The age,  sex, category and information regarding experience as  HCW,  previous  con- tact with TB patients (defined as contact within conversational distance with a patient who had a smear-positive case or clinical evidence of tuber- culosis) were collected. Information on previous travels to other countries was obtained as part   of the medical evaluation. The countries were categorized according to TB incidence as low (<50 cases/100 000 population) and high (≥ 50/100 000 population) [7].

Data analysis

Percentages and mean and standard deviation were calculated for qualitative and quantitative vari- ables, respectively. The data were used to test the null hypothesis H0 of no association between each of the possible risk factors studied (qualitative variables) and the presence of latent tuberculosis. For the same purpose, in the quantitative variables Student’s t test and Wilcoxon Mann—Whitney were used, respectively, for the ‘‘age’’ and period work- ing in public health. For hypothesis tests testing the significance level was 0.05.

Results

Of the 202 HCWs with pre-employment evaluation, 128 (63.4%) were nurses, 42 physicians and 32 technicians, with a mean age of 39.0 years (with a standard deviation of 6.5 years), and 144 (71.3%) were females. The staff  had  17.0  ( ± 7.2)  years of experience in healthcare, and 27% had direct contact with patients with suspected or confirmed tuberculosis, with contact occurring between 5 and 10 years before for 36 HCWs, within the last five years for 11 HCWs and more than 10 years before for seven HCWs. The percentage of HCWs that traveled outside, mainly for work, for a minimum of one year was 46.8%.

TST results were positive for 14 subjects (6.9%), of which 11 were nurses and 12 were females. Previous contact with patients with tuberculosis was reported by five HCWs (35.7%), and of the nine HCWs that had traveled abroad, seven had gone to countries with a high incidence of tuberculosis.

QFT-G results were positive in six subjects (3.0%), including three nurses and two physicians, and five (83.3%) of the positive subjects were females. It is remarkable that the HCWs with positive results were older than those with negative results (44.5 vs. 38.9 years) (p < 0.05) and had more experience as HCWs (21.7 vs. 16.8 years)   (p > 0.05). Positive subjects mentioned more fre- quently that they had had direct contact with tuberculosis patients (83.3% vs. 25%) (p < 0.05) and previous visits to countries with high TB incidence (p < 0.05).

Among those subjects with positive TST, 64.3% and 35.7% tested negative and positive, respectively, to QTF-G. Within those subjects with positive QTF-G, 83.3% tested positive in the  TST  test  (Fig. 1). No active tuberculosis was diagnosed in HCWs.

Figure 1 Description of study population according Mantoux and QTF-G results.

Discussion

To our knowledge, this is the first report on the prevalence of LTBI in Cuban  HCWs  using  both the TST and QFT-G tests. The prevalence of LTBI found in the current study is lower than the prevalence previously described in Cuban HCWs [10,11], especially when considering the results of QuantiFERON-TB Gold. These results can be explained by the characteristics of the studied subjects, which come from different healthcare facilities across the country. The factors influencing TB transmission risks in healthcare facilities are the incidence of the disease in the population, the adherence to infection control practices and the administrative controls implemented [2].

The associations of LTBI with age, experience as HCW, previous contact with TB patients and travel- ing to countries with high TB incidence have been previously reported. In the study of Borroto S et al. [11] on Cuban HCWs, the contact with TB patients was found to be a main predictor of infection, with an annual risk of TB infection of 1.4%. Khana P et al. [6] showed that nurses born in countries with high TB incidence and with more than two years experience working in healthcare have more frequent positive QuantiFERON results than other groups.

Alvarez León et al. [3] identified age and con- tact with TB as main risk factors associated with latent tuberculosis in Spanish HCWs when using QFT-G test, while the TST test did not find associa- tion with other factors (age, working in a high risk department, collaborating in high risk procedures and previous contact with TB patients). Our results did not find an association between the variables under study and the TST results (Table 1).

Table 1 Results of univariate analysis of variables according TST and QuantiFERON results in medical staff.

Variables
TST results
QuantiFERON results
Positive Negative P value Positive Negative P value
n = 14 n = 188 n = 6 n = 196
Profileª
Nurse 11 (8.6) 117(91.4) 0.45 3 (2.3) 125 (97.7) 0.7
Physician 2 (4.8) 40 (95.2) 2 (4.8) 40 (95.2)
Ancillary 1 (3.1) 31 (96.9) 1 (3.1) 31 (96.9)
Sexª
Female 12 (85.7) 132 (70.2) 0.18 5 (83.3) 139 (70.9) 0.5
Male 2 (14.3) 56 (29.8) 1 (16.7) 57 (29.1)
Age (years)b 39.9 (5.2) 39.0 (6.6) 0.6 44.5(6.6) 38.9 (6.5) 0.037
Time as healthcare worker (years)b 17.7 (5.8) 16.9 (7.3) 0.7 21.7 (6.7) 16.8 (7.2) 0.09
Previous contact with TB patientª 5 (35.7) 49 (26.1) 0.45 5 (83.3) 49 (25.0) 0.006
Travel to countriesª
Low incidence TB 2 (14.3) 51 (27.1) 0.27 0 53 (27.0) 0.014
High incidence TB 7 (50.0) 36 (19.1) 5 (100) 36 (19.0)

ª Data presented as No (%). b Data presented as means (standard deviation).

Considering that the incidence of tuberculosis in Cuba is low, which determines a low probabil- ity of exposure or contact with TB patients, the reference of traveling to high-incidence countries must be considered as a risk factor of outstand- ing importance. Approximately 50% of Cuban HCWs travel overseas mainly for working purposes [12].

The fact that almost all of the Cuban population receives Calmette Guérin vaccine (BCG) is an important issue that should be considered in the analysis of our results [9,11]; nevertheless, the cut- off point used for the diagnosis of LTBI reduces the likelihood of a vaccine effect in the current TST results [13—15].

The main limitation of our study is that the Cuban workers are coming from different institutions and provinces with different risks of tuberculosis, which does not allow for extrapolation of the results. Nevertheless, the information is valuable to describe the prevalence and factors associated with LTBI, especially the history of traveling to countries with a high TB incidence. We consider it advisable to introduce the QTF-TB Gold test in the diagnosis armamentarium used in the national program to control TB.

 

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