Factors associated with the high tuberculosis case rate in an urban area.

SETTING: The Rotterdam region, the Netherlands, 1995-2006. OBJECTIVE: To identify factors associated with the high tuberculosis (TB) case rate in an urban area. DESIGN: Municipalities were divided into urban and semi-urban/rural municipalities. We compared the characteristics of TB cases and stratified case rates according to age group, immigrant status and place and time of infection between the two areas. RESULTS: The TB case rate in urban municipalities was 3.8-fold higher than in semi-urban/rural municipalities. After stratification for country of birth, the rate ratios were lower (1.7 for immigrants and 2.8 for non-immigrants). Immigrants had most frequently acquired their infection abroad (47% of urban and 62% of semi-urban/rural immigrant cases). In 40% of urban cases and 27% of semi-urban/rural cases, the infection was recently acquired in the Netherlands, translating into a 5.7-fold higher recent transmission case rate for the urban population. CONCLUSIONS: The high urban TB case rate was related to the high proportion of urban immigrants who frequently reactivated an infection acquired abroad. Recent transmission also contributed to a substantial part of the TB caseload in urban municipalities among both urban immigrants and non-immigrants. The authors propose a package of targeted interventions to address the identified factors associated with the high urban TB case rate.

Transmission classification model to determine place and time of infection of tuberculosis cases in an urban area.

We conducted a population-based study in the Rotterdam region of The Netherlands to determine the place and time of infection of tuberculosis (TB) cases using conventional epidemiological and genotyping information. In particular, we focused on the extent of misclassification if genotyping was not combined with epidemiological information. Cases were divided into those with a unique mycobacterial DNA fingerprint, a clustering fingerprint, and an unknown fingerprint. We developed transmission classification trees for each category to determine whether patients were infected in a foreign country or recently (2 years) infected in The Netherlands. Of all TB cases during the 12-year study period, 38% were infected in a foreign country, 36% resulted from recent transmission in The Netherlands, and 18% resulted from remote infection in The Netherlands, while in the remaining cases (9%) either the time or place of infection could not be determined. The conventional epidemiological data suggested that at least 29% of clustered cases were not part of recent chains of transmission. Cases with unknown fingerprints, almost all culture negative, relatively frequently had confirmed epidemiological links with a recent pulmonary TB case in The Netherlands and were more often identified by contact tracing. Our findings highlight the idea that genotyping should be combined with conventional epidemiological investigation to establish the place and time of infection of TB cases as accurately as possible. A standardized way of classifying TB into recently, remotely, and foreign-acquired disease provides indicators for surveillance and TB control program performance that can be used to decide on interventions and allocation of resources.

Completeness of notification of tuberculosis in The Netherlands: how reliable is record-linkage and capture-recapture analysis?

The aim of this study was to describe a systematic process of record-linkage, cross-validation, case-ascertainment and capture-recapture analysis to assess the quality of tuberculosis registers and to estimate the completeness of notification of incident tuberculosis cases in The Netherlands in 1998. After record-linkage and cross-validation 1499 tuberculosis patients were identified, of whom 1298 were notified, resulting in an observed under-notification of 13.4%. After adjustment for possible imperfect record-linkage and remaining false-positive hospital cases observed under-notification was 7.3%. Log-linear capture-recapture analysis initially estimated a total number of 2053 (95% CI 1871-2443) tuberculosis cases, resulting in an estimated under-notification of 36.8%. After adjustment for possible imperfect record-linkage and remaining false-positive hospital cases various capture-recapture models estimated under-notification at 13.6%. One of the reasons for the higher than expected estimated under-notification in a country with a well-organized system of tuberculosis control might be that some tuberculosis cases, e.g. extrapulmonary tuberculosis, are managed by clinicians less familiar with notification of infectious diseases. This study demonstrates the possible impact of violation of assumptions underlying capture-recapture analysis, especially the perfect record-linkage, perfect positive predictive value and absent three-way interaction assumptions.

[Delay in the diagnosis of tuberculosis]. / Vertraging bij de diagnostiek van tuberculose.

In five patients, a 46-year-old Surinamese man, a 45-year-old Dutch barkeeper, a 41-year-old woman from Eritrea, and an 18-year-old Afghan woman and her 43-year-old mother, tuberculosis was diagnosed and treated after a considerable delay. Such a late diagnosis and subsequent treatment is not uncommon for tuberculosis as the symptoms, physical examination, laboratory tests, imaging techniques and bacteriological results are often not very specific. However under certain circumstances, tuberculosis (including the extrapulmonary manifestations) should be considered at an earlier stage, especially among certain risk groups such as the homeless, drug addicts, immigrants and asylum seekers. In the five patients discussed the causes of delay were identified as: delay caused by the asymptomatic phase of the disease, the patient's delay in presenting, a delay on the part of the physician, a delay in diagnostic confirmation and a delay in the treatment.