Valérie Schwoebel 1, Hans L. Rieder 2, John M. Watson 2, Mario C. Raviglione 4 for the working group for uniform reporting on tuberculosis cases in Europe

1 European Centre for the Epidemiological Monitoring of AIDS, Saint-Maurice, France

2 International Union Against Tuberculosis and Lung Disease, Paris, France

3 Public Health Laboratory Service Communicable Disease Surveillance Centre, London, United Kingdom

4 Tuberculosis Research and Surveillance Unit, Global Tuberculosis Programme, World Health Organization, Geneva, Switzerland

Introduction

The most readily accessible and informative indicator of morbidity caused by tuberculosis is the incidence of disease. In Europe, differences between countries in case definitions, reporting systems, and information collection make comparison difficult (1,2) and hamper analysis of time trends, identification of common population groups in whom the incidence is high, and the international coordination of efforts to control tuberculosis in Europe.

This paper summarises recommendations for uniform reporting on tuberculosis cases made by a working group set up in 1994 following a meeting on tuberculosis control in low prevalence countries. The meeting had been organised jointly by the World Health Organization (WHO), the European Region of the International Union Against Tuberculosis and Lung Disease (IUATLD), and the Royal Netherlands Tuberculosis Association (KNCV). The working group consisted of representatives of governmental and non-governmental organisations of 37 countries of the WHO European Region, including all 15 countries of the European Union. The complete report of the recommendations with the list of all members of the working group is published in the European Respiratory Journal (3).

Case definition

For countries where level II laboratories (capable of identification of Mycobacterium tuberculosis complex [4]) are routinely available, a "definite" case of tuberculosis is a case with culture confirmed disease due to M. tuberculosis complex. In countries where routine culturing of specimens cannot be afforded or expected, a patient with sputum smear examinations positive for acid-fast bacilli is also considered to be a definite case.

Reporting is also required for "other than definite" cases which meet both of the following conditions: 1) a clinician's judgement that the patient's clinical and/or radiological signs and/or symptoms are compatible with tuberculosis, and 2) a clinician's decision to treat the patient with a full course of antituberculosis treatment.

Definite and other than definite cases should be reported separately to enable definite cases and their proportion among all cases to be internationally compared.

Data collection, reporting and analysis

Most countries in Europe have legal provisions for mandatory reporting by physicians. Nevertheless the legal requirement to report cannot usually be enforced. Since there are fewer level II laboratories (4) than there are physicians potentially seeing cases, the working group recommends that national health authorities make reporting of tuberculosis mandatory for both physicians and laboratories. Laboratories should be asked to report each pathogenic isolate of M. tuberculosis complex.

Local/regional level: All patients started on anti-tuberculosis medication should be notified by their physician to the local health authorities within one week. For this initial report, the full name, date of birth and sex of the patient, presumptive diagnosis, date of starting treatment, and name and address of the reporting physician is enough to ensure that contact tracing can start in collaboration with the physician. These preliminary reports could be sent, say, weekly, to the national health authorities to allow the early detection of changes in time trends.

Local health authorities should seek further information from reporting physicians by means of an extended reporting form. This information should be returned to the local health authority within a maximum of three months after a suspected case is reported, providing sufficient time to classify definitively a suspect as a notifiable case of tuberculosis. Laboratories that identify M. tuberculosis complex should provide information about the bacteriological findings together with the name and address of the physician and the full name, date of birth, and sex of the patient to enable further information to be obtained from the physicians about cases not previously reported.

Depending on the resources available, local health authorities have the responsibility to collect information, definitively classify cases, link information from different sources (laboratories, physicians), follow up cases not previously reported by one of the sources, complete missing information and eliminate duplicate reporting. They should send individual (non-aggregate) information to the national authorities, with or without name or other identifier depending on the country's legal requirements, continually or at least quarterly. In the absence of sufficient local resources, named (or suitably coded) data would have to be sent to the national health authorities .

National level: Public health authorities should regularly analyse, interpret, and publish collected surveillance data. Data from the local/regional level should be aggregated at least quarterly for the publication of preliminary national statistics. It will usually be sufficient for final summary reports to be produced annually. Ideally, analysis should be carried out according to the year when treatment began, provided the calendar year is closed at the end of the first quarter in the following year, to allow sufficient time for the case to be verified.

Essential variables

Date of starting treatment - To obtain accurate estimates of incidence, the date of onset of disease or the date of diagnosis should be known, but this may often be difficult to fix in time. The date of starting treatment constitutes a reasonable proxy and the working group recommends that it should be recorded in all cases. For pulmonary tuberculosis, the date when treatment starts will usually coincide with the date when a positive sputum smear result is obtained from the laboratory or, in sputum smear negative cases, when the clinician has gathered enough clinical and/or radiological evidence for the diagnosis to justify starting treatment. If the date of starting treatment is unavailable, the date when the case was notified may be substituted. For cases that never received treatment - for example, postmortem diagnoses - the date of diagnosis should be substituted.

Place of residence - Recording the place of residence of a tuberculosis patient is essential for public health action. After appropriate aggregation, the place of residence also provides information about differences in disease frequency in different parts of the country. The place of residence should be where the patient was living at the time treatment began. In cases of homeless people, migrants, and detainees, the place of residence within the country during the previous three months might be used. For European comparison, aggregation by country will usually suffice.

Age, sex, and country of birth - Date of birth and sex are variables that should be known for each patient. In view of the increasing importance of tuberculosis among immigrants and other foreigners in European countries, the Task Force on Tuberculosis Control and International Migration (5) identified country of birth as the additional variable that should be collected routinely. Country of birth may not always be the most relevant variable and some countries may also collected data on ethnicity, citizenship, or citizenship of parents.

Site of disease - It should always be recorded. Patients may have multiple sites of disease and it is therefore recommended that at least two sites, a major and a minor site, when applicable, should be recorded. The use of the following classification will enable consistent data to be collated and analysed within and between countries:

* Pulmonary tuberculosis is defined as tuberculosis of the lung parenchyma and the tracheobronchial tree only. It is proposed that pulmonary tuberculosis, if present, should always be listed as the major site whatever other site may additionally be affected. Extrapulmonary tuberculosis is then defined as tuberculosis affecting any site other than pulmonary.

* Pleural tuberculosis is defined as extrapulmonary tuberculosis and is tuberculous pleurisy only, with or without effusion.

* Lymphatic tuberculosis includes tuberculosis involving the lymphatic system. Because of the intrathoracic manifestations of tuberculosis in children and in patients with HIV infection, lymphatic tuberculosis is preferably further differentiated into intrathoracic and extrathoracic lymphatic tuberculosis.

It is proposed here that if tuberculosis in children involves both the lung parenchyma and a lymphatic component, the case should be classified as pulmonary (major site) and intrathoracic lymphatic (minor site) tuberculosis.

* Tuberculosis of the bones and/or joints should be subdivided into:

- tuberculosis of the spine

- tuberculosis of bones/joints other than spine

* Tuberculosis of the central nervous system (CNS) should be subdivided into:

- tuberculous meningitis

- tuberculosis of the CNS other than meningitis

* Tuberculosis of the genitourinary system includes tuberculosis of kidney, ureter, bladder, and male and female genital tracts.

* Peritoneal/digestive tract tuberculosis includes tuberculosis of the peritoneum with or without ascites and tuberculosis of the digestive tract.

* Other extrapulmonary sites, including laryngeal tuberculosis.

* Disseminated tuberculosis includes miliary tuberculosis, tuberculosis in which M. tuberculosis complex has been isolated from blood, and tuberculosis of more than two organ systems. If one of the affected sites is the lung parenchyma, the case should be classified as having both pulmonary and disseminated tuberculosis. Miliary tuberculosis is classified as both pulmonary and disseminated.

For European comparison, cases should be classified into three groups: pulmonary tuberculosis only, pulmonary and extrapulmonary, and extrapulmonary tuberculosis only.

Bacteriological status - Information about the bacteriological status of cases must always be included. The result of culture (negative or positive for M. tuberculosis complex, not done, or pending) and the source specimen must be recorded by the physician and the laboratory. Whenever possible, further differentiation of isolates into M. tuberculosis, M. bovis, or M. africanum should also be reported. Similarly, the result of direct microscopic examination (negative or positive for acid-fast bacilli, or not done) and the source specimen providing a positive result must be reported. Cases of pulmonary tuberculosis should be divided into smear positive and smear negative cases based on direct microscopic smear examination of spontaneously produced or induced sputum. Cases positive on microscopy of material obtained from bronchoalveolar or gastric lavage only should not be considered to be sputum smear positive. Histological examination with evidence of acid-fast bacilli should be considered as positive microscopy.

Recurrent or new disease - It must be made clear for epidemiological purposes whether or not a notified case has had tuberculosis before. In reporting recurrent cases, care must be taken to ensure that chronic cases and patients that intermittently abscond and return are not repeatedly notified. Information on the existence and date of prior diagnosis of tuberculosis and on previous antituberculous chemotherapy will allow recurrent cases to be classified into relapse (previous treatment considered as adequate) and recurrence with or without previous chemotherapy.

Other variables - Additional variables such as tuberculin skin test results, results of chest radiographs, patient's citizenship, subdivision of foreigners into migrant workers, refugees/asylum seekers, and other foreigners, duration of residence within the country for patients born elsewhere, and cases not diagnosed until after death, may be collected for individual, local, or national purposes. However, completeness of case reporting is likely to be better if the information requested is kept to a minimum. Specific surveys may be used to answer more complex questions of special interest in tuberculosis control.

Conclusion

This document represents a consensus of technical recommendations to European governments on how to structure their tuberculosis surveillance systems with a view to standardisation that would allow international comparisons. The interpretation of surveillance figures must include an appreciation of the quality of data from individual countries. Most countries collect all the information considered essential to allow uniform reporting of tuberculosis cases in Europe. Most systems would thus need only minor modifications. The members of the working group, WHO, and the European Region of the IUATLD consider it essential to obtain regular surveillance data on tuberculosis from national governments, to make international comparative analyses of these data, and to distribute them to participating member states. WHO has officially invited all ministries of health of its European region to adopt the recommendations. A one year project for tuberculosis surveillance in Europe, developed by the European Centre for the Epidemiological Monitoring of AIDS in collaboration with the KNCV and funded by the Directorate General V of the European Commission, will start in 1996 based on these recommendations.

References

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2. Raviglione MC, Rieder HL, Styblo K, Khomenko AG, Esteves K, Kochi A. Tuberculosis trends in eastern Europe and the former USSR. Tuber Lung Dis 1994; 75: 400-16.

3. Rieder HL, Watson JM, Raviglione MC, Forssbohm M, Migliori GB, Schwoebel V, Gordon Leitch AG, Zellweger JP. Surveillance of tuberculosis in Europe. Eur Respir J 1996; 9:1097-1104.

4. Kubica GP, Gross WM, Hawking JE, Sommers HM, Vestal AL, Wayne LG. Laboratory services for mycobacterial disease. American Review of Respiratory Diseases 1975; 112 : 773-87.

5. Rieder HL, Zellweger JP, Raviglione MC, Keizer ST, Migliori GB. Tuberculosis control and international migration in Europe. Eur Respir J 1994; 7: 1545-53.