National surveys undertaken in the PRC from 1979–90 showed that although the prevalence of TB fell by an average of 3.3% annually during the 1980s, the notification rate represented only 30% of the total burden in the 1990s
. This was due mainly to the collapse of the public health system which particularly affected rural communities throughout the PRC
. The reduction in government expenditure in the health sector fell from 32% in 1972 to 16% in 2002. This forced many Chinese health-care facilities and providers to run as businesses, requiring patients to pay for their diagnostic tests and treatment regimens. Many patients could not afford to maintain consistent and regular treatment for the required period due to the high cost of anti-TB drugs, which may reflect the rapid increase in the prevalence of multidrug-resistant (MDR) TB
. This inadequate TB control thus reflected the heavily malfunctioning health system during this period in the PRC.
TB has been particularly hyper-endemic in the underdeveloped areas in north-western PRC for several decades. The high-prevalence in NHAR as reported in the 2000 national survey placed it as the third most prevalent autonomous region/province in PRC and 1.67 times higher than the national average (619/100,000 vs. 367/100,000). The prevalence in PRC then was 4.6 times higher than the global average prevalence for TB of 139/100,000.
Scrutiny of the data presented here indicates the average incidence in NHAR from 2005–2008 was low (61/100,000) but it is likely that the reported cases substantially underestimated the total number of patients with TB as many individuals could have remained undiagnosed. The overall distribution of high incidence counties appears to be random and could be due to different TB transmission factors occurring in these areas. For example, Longde county in south NHAR had the highest proportion of individuals waiting over six months from the onset of symptoms to seeking medical advice (15.8%) which, combined with the highest population density in NHAR and low economic level, may account for the highest recorded incidence. In contrast, Haiyuan county had some of the highest incidence rates over the 4 year period, but has one of the lowest population densities in the province suggesting that specific geographical and/or socio-economic factors may contribute to TB transmission in this county. Although the Yinchuan urban Counties have higher per capita GDP levels
, and thus would be expected to have a lower incidence of TB, they are impacted by the influx of seasonal migrants coming from more rural parts of NHAR during winter months to seek temporary employment. Further work is required to investigate the full effect that these migrants have on TB prevalence. The overall epidemic trend of notification rates in NHAR showed a gradual increase over the 4-year period. These rates appear to have fluctuated over this time with different trends observed in different counties; however, increased notification rates were observed in most counties overall. Such increased notification rates may suggest a higher rate of case identification rather than increased transmission. Similarly, several counties reported relatively low notification rates of TB compared to NHAR overall. While this could reflect lower transmission, it may equally indicate lower diagnosis rates. As this study focused on registered patient records only, subjects who failed to seek medical treatment or who were misdiagnosed, would have been missed. Accordingly, the numbers reported here likely underestimate the true disease burden attributable to TB in NHAR. Such under-reporting is an important issue since undisclosed cases will continue to spread the disease and thus may reflect the overall increase in notification rate during the 2005–2008 study period. Active screening should be undertaken to determine the true prevalence and incidence of TB in NHAR.
The low TB incidence evident in the very young (0–9 years of age) in NHAR reflects the difficulty of establishing a definitive diagnosis in this age group
. Interestingly, there was a small peak observed in young adult age (20–24 years of age) which may reflect high transmission rates. The higher incidence observed in some adult age categories could also reflect the different socio-economic status of these groups, as well as age-related immunological factors
. The results of this survey support previous studies that showed significantly higher TB incidence in males than females, which may reflect a genuine sex difference in TB susceptibility
[18, 19], or behavioural differences
The length of time that patients took to seek medical attention (patient delay) and the delay in diagnosis is of concern in NHAR. More than 25% of all cases wait over three months to seek medical attention and 30% of these wait more than 6 months. Such patient delay was found to be particularly high in specific counties. The reason for patient delay in these counties is unknown but may reflect a lack of TB awareness and/or socio-economic considerations such as the cost of initial diagnosis and the distance patients needed to travel for medical attention. Although DOTS is free of charge in NHAR, it is only implemented once a clear diagnosis has been made. These factors are critical issues for the control of TB in NHAR. The lack of treatment increases morbidity and mortality at the patient level; this also increases exposure at the community level as patients remain infectious as long as they are untreated.
The prolonged time of treatment-to-cure observed in this study likely reflects failure of the DOTS program at the community level. As of the end of this study period, a total of 5394 patients were recorded as currently on treatment and, of these 58% had been receiving treatment for over two years. Many factors may contribute to this, including the difficulty in surveillance, due to large distances between patient residence and TB clinic, and chemotherapy non-compliance. Inadequate TB awareness in the community coupled with poor knowledge and/or training of local health workers may increase community exposure and fuel TB transmission. Thus evaluation of these factors should be a priority in order to develop new control strategies and identify early-stage cases for successful treatment by the DOTS program and minimise the transmission of infection.