RATIONALE FOR SURVEILLANCE
About one-third of the world's population is infected by Mycobacterium tuberculosis. Between 7 and 8.8 million new cases occur each year, 95% in developing countries; some 3.3 million cases of tuberculosis are notified each year. Projections into the next century suggest that the impact of tuberculosis will increase if no adequate control is established immediately in all countries.
The overall objective of tuberculosis control is to reduce morbidity, mortality and transmission of the disease until it no longer poses a threat to public health. To achieve this objective, the 1991 World Health Assembly endorsed the following targets for global tuberculosis control:
• successful treatment for 85% of the detected new smear-positive cases
• detection for 70% of smear-positive cases by the year 2000
Surveillance of tuberculosis helps to monitor the course of the tuberculosis epidemic, and patient cohort analysis is used to evaluate treatment outcomes.
RECOMMENDED CASE DEFINITIONS
DEFINITIONS OF WHO/IUATLD
(INTERNATIONAL UNION AGAINST TUBERCULOSIS AND LUNG DISEASES)
1. Site and bacteriology
Pulmonary tuberculosis, sputum smear positive (PTB+)
• Tuberculosis in a patient with at least two initial sputum smear examinations (direct smear microscopy) positive for Acid-Fast Bacilli (AFB), or
Pulmonary tuberculosis, sputum smear negative (PTB-)
• Tuberculosis in a patient with one sputum examination positive for acid-fast bacilli and radiographic abnormalities consistent with active pulmonary tuberculosis as determined by the treating medical officer, or
• Tuberculosis in a patient with one sputum specimen positive for acid-fast bacilli and at least one sputum that is culture positive for acid-fast bacilli.
Tuberculosis in a patient with symptoms suggestive of tuberculosis and having one of the following:
• Three sputum specimens negative for acid-fast bacilli
• Radiographic abnormalities consistent with pulmonary tuberculosis and a lack of clinical response to one week of a broad-spectrum antibiotic
• Decision by a physician to treat with a full curative course of anti-tuberculous chemotherapy
Pulmonary tuberculosis, sputum smear negative, culture positive
Tuberculosis in a patient with symptoms suggestive of tuberculosis and having sputum smear negative for acid-fast bacilli and at least one sputum that is culture positive for M. tuberculosis complex
• Tuberculosis of organs other than lungs: pleura, lymph nodes, abdomen, genito-urinary tract, skin, joints and bones, tuberculous meningitis, etc.
• Diagnosis should be based on one culture positive specimen from an extra-pulmonary site, or histological or strong clinical evidence consistent with active extra-pulmonary tuberculosis, followed by a decision by a medical officer to treat with a full course of anti-tuberculous therapy
• Any patient diagnosed with both pulmonary and extra-pulmonary tuberculosis should be classified as a case of pulmonary tuberculosis
2. Category of Patient
New case: A patient who has never had treatment for tuberculosis or took anti-tuberculous drugs for less than 4 weeks.
Relapse case: A patient previously treated for tuberculosis and declared cured by a medical officer after one full course of chemotherapy, but who reports back to the health service bacteriologically positive (smear or culture).
In addition to these definitions, European countries also report cases as "definite" (confirmed by culture of M. tuberculosis complex or by sputum smear examinations positive for acid-fast bacilli) or "other than definite" (based on a clinician's impression of symptoms, signs and radiological findings and decision to treat the patient with a full course of anti-tuberculosis treatment).
RECOMMENDED TYPES OF SURVEILLANCE
Registration of diagnosed cases at district level.
Quarterly reports on case notifications and cohort analysis of treatment outcomes (at peripheral, intermediate, and central level).
RECOMMENDED MINIMUM DATA ELEMENTS
Case notifications by category
• Number of new pulmonary sputum smear positive cases
• Number of pulmonary relapse cases
• Number of new pulmonary sputum smear negative cases
• Number of new extra-pulmonary cases
• Number of new pulmonary sputum smear positive cases by age and gender (suggested age groups: 0-14,15-24, 25-34, 35 - 44, 45-54, 55-64, 65+ years)
Treatment results for new sputum smear positive cases:
(usually as a percentage of all new sputum smear positive cases registered during the same period of time):
• Number of cases who converted to negative after initial phase of treatment
• Number of cases cured (i.e., completed treatment and at least 2 negative sputum smear results during the continuation phase of treatment, one of which occurred at the end of treatment)
• Number of cases who, after smear conversion at the end of initial phase of treatment, completed treatment, but without smear results at the end of treatment
• Number of cases who died (regardless of cause)
• Number of cases who failed treatment (i.e., became positive again or remained smear positive, 5 months or more after starting treatment).
• Number of cases who interrupted treatment/defaulted (i.e., did not collect drugs for 2 months or more after registration)
• Number of cases who were transferred out (i.e., transferred to another reporting unit and results not known)
Note: In countries routinely using culture as a diagnostic tool, the treatment results may be based on a second culture obtained during the continuation phase of treatment.
RECOMMENDED DATA ANALYSIS, PRESENTATION, REPORTS
Analysis of geographical area (district) quarterly reports
• Treatment success rate: number of cases cured, plus patients who completed treatment, as a ratio of all cases registered during the same period of time
• Quality of diagnostic services: ratio of new sputum-smear positives to all pulmonary cases
Presentation and reports Graphs:
• Case notification rates over several years by geographical area, regions, country.
• Case notification rates (new sputum smear positives) by age and sex
• Case detection rate: ratio of the tuberculosis cases detected by the national tuberculosis control programme to the number of cases estimated to have occurred in the country
Describe quarterly reports by case finding and treatment outcomes.
PRINCIPAL USES OF DATA FOR DECISION-MAKING
• At local level: ensure that appropriate treatment services are offered, contact tracing is carried out, local outbreaks are recognized, and local epidemiology is monitored
• At national level: facilitate monitoring of the epidemiology of the disease and of the performance of treatment programmes (ability of a National Tuberculosis Programme to detect tuberculosis cases, diagnose sputum positive cases, treat tuberculosis cases successfully); and facilitate planning for programme activities (e.g., securing drug supply, lab supply, etc.)
• At international level: examine trends over time and make inter-country comparisons with the aim of coordinating control efforts
See Regional Communicable Disease contacts on section "Communicable disease contacts in Regional Offices".
Headquarters: 20 Avenue Appia, CH-1211 Geneva 27, Switzerland
Communicable Diseases Surveillance (CDS)
E-mail: firstname.lastname@example.org / Surveillancekit@who.ch
Tel: (41 22) 791 2598
Fax: (41 22) 791 4199