Case definitions and classification.
The following case definitions and classification were used.
Definite TB case in countries where culture and identification of M. tuberculosis complex were routinely available: a patient with culture-confirmed disease due to M. tuberculosis complex; definite TB case in countries where culturing of specimens was not feasible: a patient with sputum smear positive for acid-fast bacilli.
Other-than-definite TB case met the two conditions:
• a judgment that the patient’s clinical and/or radiological signs and/or symptoms are compatible with tuberculosis;
• a clinician’s decision to treat the patient with a full course of anti-tuberculosis treatment.
New case: a patient who has never had TB previously.
Recurrent case: a patient who has had a previous episode of TB.
Drug resistance: a resistance at the start of treatment to one drug or any combination with resistance to the other three drugs. Concomitant resistance to at least isoniazid and rifampicin, with or without resistance to ethambutol and streptomycin, is defined as multidrug resistance (MDR).
Figures and trends
363 521 cases of TB were notified in the WHO European Region in 1998, of which 62% (77,7 per 100 000) in the Eastern Europe and more than a half of the cases were notified in the Russian Federation. Notification trends in 1995-1998 differed by country profiles. When comparing rates in 1998 with 1995, notification rates had decreased from 14,2 to 13,0 in the West (-9%), increased from 45,4 to 46,7 in the Centre (+3%) and increased markedly in the East from 56,9 to 77,7 per 100 000 (+37%).
In many Western European countries trends were affected by increasing numbers of cases notified in patients of foreign origin. In the Centre notification rates decreased by 8% or more in Hungary, Macedonia, Poland, Slovakia, Slovenia and Yugoslavia, decreased by 2% in the Czech Republic and increased in Turkey by 6%, Romania by 13%, Bulgaria by 34%, Bosnia-Herzegovina by 36%. In the East notification rates increased by 37% overall, ranging from 6% in Moldova to 95% in Kazakhstan. Increases in TB notifications in these countries reflected a combination of social-economic difficulties, disruption of health services including TB control programmes, delays in diagnosis and treatment and inadequate treatment.
New and recurrent cases
Data on previous TB diagnosis were available in 43 countries: 88% of notified cases were new cases, 10% recurrent cases and 2% had no information. The proportion of recurrent cases was 10% in the West, 13% in the Centre and 9% in the East. Differences between countries could be due to the differing recommendations for including recurrent cases in TB notifications and on the adherence of these recommendations, due to inclusion in notifications of prevalent cases under treatment and due to under-notification of recurrent cases.
Sex and age
Among the 40 countries which provided information on sex, 64% of the TB cases notified were male. Sex ratio was 1,8 overall, ranging from 1,6 in the West to 1,7 in the East and to 2,1 in the Centre. The sex ratio increased with age and peaked for the 45-64 years age group. For the whole WHO/EURO Region , it was 1,2 among patients under 15 years of age, 1,8 between 15 and 44 years, 2,7 between 45 and 64 years and 1,8 over 64 years. The age group 15-44 years represented 43% of cases notified in the West, 47% in the Centre and 61% in the East. Age group 64 years and over represented 21% of cases in the West, 17% in the Centre and 7% of cases in the East.
Age specific notification rates were highest in the age group 65 years and over in the West, were similar from age 35 in the Centre and were highest in the age group 25-34 in the East. The highest notification rate observed in the older age group in the West was mainly due to reactivation of old TB-infection.
In the West, age specific notification rates among males were relatively stable across the age groups 25-34 to 55-64 and were highest among the elderly. In females, rates were highest in the age group 65 years or over. In the Centre, rates increased rapidly after age 14 in males but less rapidly in females. In the East, rates peaked in the 25-34 age group in both sexes, with a second peak in group 45-64 among males, and decreased in older age groups. Higher notification rates in males compared to females observed in all countries could reflect a higher prevalence of TB-infection in males and partly by an under-reporting of females in some countries due to differences in access to health services.
Information on TB patients of foreign origin was more frequently available from countries in Western Europe: the proportion of cases in foreign patients was 27% in the West, 1% in the Centre and 4% in he East. In ten countries in the West, patients of foreign origin represented more than 40% of notified cases (including Denmark, Iceland, Norway and Sweden). In the population of foreign origin, the notification rates peaked in the 25-34 year of age group, at a higher level in males, and in the age group over 64 years. 47% of foreign patients were born in six countries: Somalia (12%), India (11%), Pakistan (10%), Morocco (6%), Yugoslavia (4%) and Bosnia-Herzegovina (4%).
Site of disease
Information on site of the disease was provided by 42 countries. The proportion of pulmonary/respiratory case was 75% in the West, 88% in the Centre and 90% in the East. Information on both major and minor site of the disease was provided by 12 countries (including Iceland, Norway and Estonia): pulmonary TB was reported in 80.3%, pleural TB in 10.6% and lymphatic extrathoracic TB in 4.8% of the patients. All other sites were reported less than 2% of cases: meningeal TB in 0.7%, spine TB in 0.7%, bone/joint TB in 1.0%, genital-urinary TB in 1.3%, peritoneal/digestive TB in 1.0% and disseminated TB in 1.2% of the patients.
The site of the disease varied by age group. The proportion of pulmonary TB was higher among patients aged over 15 years, lymphatic intrathoracic TB and meningeal TB in children under 15 years, pleural TB among children less than 15 years and 15-44 years old. Among patients over 15 years of age, women were 1,8 times more likely than men to have extrapulmonary TB without pulmonary localisation. In patients of foreign origin, extrapulmonary TB was more frequent than in nationals (37% vs 18%) while pulmonary TB was less frequent (63% vs 82%).
Bacteriology surveillance results
Data by culture result were provided from 38 countries. Overall, 50% of the TB cases were culture confirmed: 57% in the West, 50% in the Centre and 54% in the Baltic countries. In countries providing individual data, proportions of culture positive cases were higher among pulmonary cases compared to extrapulmonary cases in the West (63% vs 50%), in the Centre (61% vs 9%) and in Estonia (68% vs 37%).
The overall proportion of culture positive cases was similar in the 21 countries using culture only (49%) and in the ten countries using both culture and sputum smear (51%) to classify cases as definite.
The overall proportion of pulmonary cases with positive sputum smear was higher in the Centre (52%) compared to the West (41%) and the East (29%). Among pulmonary cases with positive culture, the proportion of cases with positive sputum smear was 67% in the Centre and East and 53% in the West.
Around two thirds of all notified cases with information on site of TB were bacteriologically confirmed (West 64%, Centre 66%, Estonia 68%).Proportions of bacteriologically confirmed cases among pulmonary TB cases were 75% overall (West 73%, Centre 76%, Estonia 71%).
Drug resistance surveillance results
Drug susceptibility testing (DST) results were provided from 18 Western, 8 Central and the three Baltic countries.
In the 18 countries with at least 50 TB cases notified in 1998, the overall proportions of drug resistant cases were higher in the Baltic countries: for isoniazid 13-30% in Baltic countries and 1-8% in the other countries; for rifampicin 7-20% in the Baltic countries and 0-2.5% in the other countries; for ethambutol 2-19% in Baltic countries and 0-2% in the other countries; for streptomycin respectively 12-35% and 1-12%. Proportion of multidrug resistant cases were 6-18% in the Baltic countries and 0-2.2% in the other countries.
Among cases with DST results, the proportion of previously treated cases were 18-22% in the Baltic countries and 7-21% in the other countries. In the Baltic countries proportions of cases resistant to isoniazid were 12-25% among cases never treated and 17-50% among cases previously treated and in the other countries respectively 0.7-7.0% and 0-18%. Proportions of MDR cases among cases never treated were 5-15% in the Baltic countries and below 1% in the other countries.
Drug resistance among patients never treated and born in the country was analysed in individual data available from 11 countries. In Estonia, proportions of drug resistant cases were slightly higher among patients under 35 years of age compared to older patients (36% vs 20% for isoniazid and 23% vs 12% for rifampicin). In the other countries , the proportions of resistant cases were higher for isoniazid in patients under 35 years of age (3.2%) compared to older patients (2.3%) and were similar in the two age groups for rifampicin and for MDR. The higher level of drug resistance observed among younger patients in Estonia seems to indicate a high level of transmission of drug resistant tubercle bacilli. High resistance levels among both never treated and previously treated cases in the Baltic countries indicated that resistant M. tuberculosis strains have emerged and have been transmitted in the population as a consequence of suboptimal performance of TB treatment programmes. The results demonstrate that drug resistance surveillance as a part of the TB notification system is feasible and can provide a relevant contribution to the evaluation of TB programmes.
Euro TB. Surveillance of tuberculosis in Europe. WHO Collaborating Centre. Report on tuberculosis cases notified in 1998 (www.eurotb.org)