Some aspects of TB infection control in TB centers as evaluated in this study appeared inadequate in Henan province of China. The prevalence of LTBI and TB disease among HCW was higher than observed in the national TB prevalence survey in 2000 . The LTBI prevalence of 56% among medical staff was higher than the LTBI prevalence of 47% (using a cut-off point of 6 mm) in the general population group of 15 years or older from the survey in 2000. So even with a higher TST cut-off point, the estimated prevalence of LTBI amongst HCW was still higher than the prevalence in the general population group of 15 years or older in a survey conducted five years earlier. We observed a TB disease prevalence of 5.3/1000 among HCW compared to 3.0/1000 in the 15-59 year old age group in the prevalence survey. The age- and sex-stratified prevalence in the 2000 survey were applied to calculate the expected number of cases in 2005 in HCW. The calculation indicated 12 expected active TB cases but instead our study found 20 cases, which was much higher than estimated (RR = 1.67, 95%CI = 1.02-2.57).
Studies elsewhere showed varying LTBI rates amongst HCW [7, 8, 20, 21, 23]. Our results from Henan province showed high LTBI rates amongst HCW similar to other studies in low and middle income countries and compared well with an average LTBI prevalence of 54% among HCW . The prevalence of LTBI among HCW in high-income countries was generally lower [24, 25]. Our study results are also consistent with studies that show an increasing prevalence of LTBI with increasing age, work locations with higher exposure to TB patients (especially TB outpatient clinics, inpatient wards, and X-ray departments), and longer duration of employment at the health care facility [7, 8, 20, 23]. In our study, working at a TB center at the prefecture level and presence of an inpatient ward at the TB center were associated with a higher LTBI prevalence among staff members. At prefecture level, all TB centers had TB clinics and inpatient wards. Patients with more severe TB disease likely attend a prefecture TB center for medical care, which may increase the exposure to TB at prefecture level. Although the association of male sex with increased M. tuberculosis infection risk has been reported , we did not observe this (OR = 1.1, 95% CI: 0.9-1.3). However, we did observe that male smokers had an increased prevalence of TB disease compared with non-smokers, as shown before .
This study suggests that nosocomial transmission of TB is an important occupational problem among HCW. The reduction of this risk should be a priority. Occupational contracted TB can lead to the loss of skilled workers, and this can adversely impact on health care services in the long term. Medical workers may also avoid working with TB centers due to the high risk of TB transmission to HCW. TB amongst HCW can have serious, and even fatal, consequences. This problem is particularly serious with MDR-TB strains. Hospitals have been shown to be important focal points of MDR-TB transmission, resulting in explosive outbreaks [27, 28]. Implementation of effective TB infection control measures can promote awareness of the disease among HCW, and help in the adoption of good practices for diagnosis and treatment of TB.
Most of the TB centers in China are in older buildings, and therefore are not designed in line with TB infection control standards . Therefore, we suggest beginning implementation of some simple yet highly effective interventions, such as fast identification of TB suspects, segregation of infectious TB patients, and education as well as training for HCW . Administrative interventions that improve the current situation in health care facilities require minimal resources and can be easily implemented. Engineering controls such as exhaust ventilation, improved natural ventilation , and the use of UV lights are also cost-effective measures to minimize the risk of TB infection . National TB control and public health authorities should focus on addressing nosocomial TB transmission as an integral part of the TB control program. HCW are essential in the fight against TB, and their health should be protected as well as that of patients. With the emergence of XDR-TB, the need to implement TB infection control measures has been reemphasized by the WHO and the Stop TB Partnership . After the study results became available, TB centers in Henan province have strengthened training on TB infection control for HCW and paid more attention to ventilation systems and adequate UV light use.
There are several limitations to our study. The trained project staff filled in the checklists for their own centers, and therefore the staff might not have been completely honest about prevailing TB infection control practices in their own centers. Even with intensive training for TST nurses, the terminal-digit preference was visible at 10, 15, and 20 mm. The preference for cut-off point of 10 mm in TST results may have caused a slight overestimation of HCW with LTBI. Our results showed that people with BCG vaccination had higher prevalence of LTBI. BCG vaccination can also lead to positive results of the TST, thus we may have overestimated the LTBI rate in BCG vaccination group. However, a couple of international reviews have reported that the influence of BCG is relatively small in the adult population, especially ≥ 10 years after BCG vaccination [8, 14]. Misclassification of BCG vaccination status may have occurred as not all of those vaccinated develop a scar. However, the presence of a BCG scar has been found to be a good indicator of BCG vaccination  and several studies reported that 95-100% people had a BCG scar after BCG vaccination [31–33] so misclassification should be limited. Exclusion of those with BCG scar did not affect results. LTBI or TB disease in a HCW may be due to infection acquired nosocomially or in the community. We were unable to differentiate between infections acquired in the community versus in the center, but LTBI prevalence in medical staff (56%) was significantly higher than that in administrative/logistic staff (42%) in the same TB center. This indicates that at least (((56-42)/56) =) 25% of LTBI in this setting could be attributed to nosocomial infection. We observed a TB disease prevalence that was much higher than observed in the 2000 survey. This may be explained by the fact that the 2000 survey used the chest fluoroscopy, which has a much lower sensitivity than the chest X-ray method, for detecting TB. Moreover, only three of the twenty TB disease cases were smear positive. It might be that we identified some TB patients at very early stage with tiny shadows at the chest X-ray, as the majority did not have any symptoms.
We are the first to report internationally on prevalence of TB infection and disease among Chinese HCW. As TB infection control was at a very early stage at the time of the study, the infection control situation in most areas of China was likely to be similar to Henan province. In a few MDR-TB project areas in China, the TB infection control policy as recommended by the WHO is now being implemented through the national TB program . TB infection control is insufficient in most areas of China. With a high TB prevalence and limited resources, China focuses largely on case detection and treatment using the DOTS strategy. In some areas, even low-cost strategies to reduce TB transmission in health-care facilities are seldomly implemented. We strongly suggest that TB infection control strategies are rapidly implemented, with priority for provinces with high anti-TB drug resistance prevalence.