Tuber&
and Lung Disease (1992) 73,322-325
Mass miniature X-ray screening for tuberculosis among immigrants entering Switzerland L. Bonvin, J. P. Zellweger TB Dispensary,
University Medical Policlinic, Lausanne, Switzerland
S U M M A R Y. Among 50 784 new immigrants entering Vaud Country, Switzerland, between 1988 and 1990,
674 abnormalities were discovered by mass miniature X-ray screening on arrival (424/43803 foreign workers, 23814512 refugees and 120469 foreign students). 2043 refugees had no radiological examination. After clinical examination, tuberculosis (TB) was considered the likely diagnosis in 256 cases, of which 132 were offered an antituberculous treatment according to the current recommendations of the Swiss Association against TB. 34 of the subjects were smear- or culture-positive (5% of all radiological abnormalities, 0.08% of all immigrants). Only 46 subjects had any clinical complaint. Among foreign workers, 0.18 % were carriers of tuberculous lesions needing a treatment; the proportion was 1.22 % among refugees. By ethnic origin, the proportion is highest among Africans (1.43%), followed by Turks (1.04%), subjects from the Middle East (0.62%), Yugoslavia (0.55%), Portugal and Spain (0.14%). Mass miniature X-ray screening for TB in immigrants from high prevalence countries entering Switzerland still detects a majority of asymptomatic cases and seems an easy means of preventing the transmission of TB to members of the same community. R I? S U M .!?. Parmi 50 784 nouveaux immigrants entrant en Suisse dans le Canton de Vaud entre 1988 et
1990,674 cliches anormaux ont CtCrecenses lors d’un depistage radiophotographique (424/43 803 travailleurs &rangers, 23814512 requerants d’asile et 1212469 Ctudiants &rangers). 2043 requerants d’asile n’ont pas subi d’examen radiologique. Aprb examen clinique, 256 diagnostics de tuberculose ont CtCretenus et un traitement antituberculeux a CtC propose a 132 sujets selon les recommandations de I’Association Suisse contre la Tuberculose. 11 s’est agi 34 fois de sujets a frottis ou a culture positifs (5% de l’ensemble des anomalies radiophotographiques, 0,08% de l’ensemble des immigrants). Seuls 46 patients presentaient une anomalie clinique. Chez les travailleurs &rangers, 0,18% Ctaient porteurs d’une lesion tuberculeuse necessitant un traitement; la proportion Ctait de 1,22% chez les requerants d’asile. Selon l’origine ethnique, la proportion est la plus ClevCechez les sujets originaires de l’hfrique (1,43%), ensuite la Turquie (1,04%), le Moyen Orient (0,62%), la Yougoslavie (0,55%), le Portugal et 1’Espangne (0,14%). Le depistage antituberculeux par la radiophotographie chez de nouveaux immigrants venant en Suisse en provenance une de pays a haute prevalence de&e encore majorite des cas paucisymptomatiques, et semble un moyen simple de prevenir la transmission de la tuberculose aux membres de la m@mecommunautk. R E S U M E N. En 50 784 nuevos inmigrantes al cant&r de Vaud en Suiza entre 1988 y 1990, se detectaron
imagenes anormales en la radiofotografia miniaturizada de masa, en 674 cases (424143 803 trabajadores extranjeros, 23814512 refugiados y 1212469 estudiantes extranjeros). 2043 refugiados no tuvieron examen radiologico. DespuCs de1 examen clinico, se planted el diagnostico de tuberculosis en 256 cases y a 132 de ellos se propuso un tratamiento antituberculoso de acuerdo a las normas de Asociaci6n Suiza contra la Tuberculosis. 34 pacientes tenian baciloscopia o cultivo positivos (5 % de todos 10s cases con anormalidades radiograficas y 0,OS % de1 total de imnigrantes.) Solo 46 sujetos presentaban sintomas clinicos.
Correspondence to: L. Bonvin, TB Dispensary, University Medical Policlinic, Rue C&r-Roux 19, 1005 Lausanne, Switzerland. 322
X-my screemng for TB
323
Entre 10s trabajadores extranjeros, un 0,18 % presentaban lesiones tuberculosas que necesitaban un tratamiento; esta proporcibn era de 1,22 % entre 10s refugiados. Segtin el origen Ctnico, la proporcih m8s elevada se encontr6 en 10s africanos (1,43 %), seguida por la de Losturcos (1,04 %) 10s originarios del Medio Oriente (O&2 %), de Yugoslavia (0,55 %), de Portugal y Espafia (0,14 %). La pesquisa de tuberculosis por radiofotografia miniaturizada de masa en 10s nuevos inmigrantes que llegan a Suiza, provenientes de paises de alta prevalencia, detecta atin una mayoria de cases asintomhticos y parece ser un medio simple para prevenir la transmisih de la tuberculosis a 10s miembros de la misma comunidad.
INTRODUCTION Screening for TB in low prevalence countries means searching for asymptomatic cases within high risk groups in order to offer curative treatment to bacteriologically positive patients and preventive chemotherapy to those with a high risk of recurrence.’ Although its use in whole populations is no longer advised,‘-’ mass miniature X-ray screening can still be used for early detection of cases among high prevalence groups.’ Until 1990, mass miniature X-ray screening was compulsory for all foreign workers and foreign students entering Switzerland (in 1991 only for workers and students entering for the first time). Since 1992, the examination has been restricted to new workers and students coming from high prevalence countries, i.e. countries other than the European Community, Scandinavia, Finland, the USA, Canada, Australia and New Zealand. Until 1991, the examination was usually carried out at the border the day of entry. From 1992 it must be done in the county of settlement within 1 week after arrival, before obtaining a licence to work. Refugees (and asylum seekers) are equally submitted to mass miniature X-ray screening. Until 1991 the examination was done within the county of settlement some days or weeks after arrival. From 1992, the examinations are carried out within the first days after arrival in newly created registration centers at the border, in order to avoid delay in detection and treatment of positive cases. All the immigrants with radiological abnormalities are referred to medical centers for further examination and treatment if indicated. We retrospectively studied the result of screening among foreign workers, foreign students and refugees screened by mass miniature X-ray between 1988 and 1990 and referred for examination to the local TB Dispensary in Lausanne, Vaud county.
MATERIAL AND METHOD All foreign workers entering Vaud county in whom mass miniature X-ray screening at the border detected an abnormality were referred to the local TB Dispensary in Lausanne for further examination and treatment. Foreign students and refugees were called to an X-ray screening at the TB Dispensary where the carriers of abnormalities were immediately looked at
and treated according to the recommendations of the Swiss Association against TB. ’ Foreign workers with radiological abnormalities were not provided with a work permit before the medical examination was carried out. According to Swiss state regulations, carriers of severe abnormalities suggestive of smear-positive TB could be refused entry to Switzerland and had to return home for examination and treatment. This regulation was suppressed in 1990. Foreign students and refugees were all examined and treated in Switzerland. TB was defined as active by the association of radiological abnormalities and positive smear or culture. Cases with radiological lesions suggestive of TB but negative smear and culture and who were never or incompletely treated before were considered as inactive TB and offered preventive or curative chemotherapy according to the size of the radiological lesions, the presence or absence of suggestive symptoms and the size of the tuberculin test (in young subjects).x,y We looked retrospectively at all cases of radiological abnormalities discovered by X-ray screening and the results of the further examination at the Dispensary.
RESULTS Between January 1988 and December 1990, 50 784 immigrants entering Vaud County were submitted to mass miniature X-ray screening: 43 803 foreign workers were screened at the border, 45 12 refugees and 2469 foreign students at the local TB Dispensary. 2043 refugees had no radiological examination (pregnant women, children under 15 or subjects changing residence immediately after arrival and escaping control). Radiological abnormalities were observed in 674 subjects (1.3%): 424 foreign workers (I%), 238 refugees (5.2%) and 12 students (0.5%). After clinical and bacteriological examination a diagnosis of TB was made in 256 cases (38 % of all abnormal X-rays). Other diagnoses were pneumonia (13%) current or prior pleural disease (7%), cardiovascular abnormalities (3 %), bronchiectasis (2%), sarcdidosis (1.5%) and benign tumors (1%). Rib, chest wall and vertebral abnormalities were 9 % whereas 20 % of X-rays were considered normal after control, usually due to overestimation of non-significant abnormalities or technical defects.
324
Tubercle and Lung Disease Table 1.
Tuberculosis
among carriers of X-ray abnormalities
Abnormal X-ray
Total TB
Students Foreign workers Refugees
12 424 238
4 156 96
Total
614
256
Among the subjects with radiological lesions suggestive of TB, 34 were smear- or culture-positive for acid-fast bacilli and 132 required treatment (preventive in 21 cases, curative in 1I I) (Table 1).
RADIOLOGICAL
APPEARANCE
50% of 674 radiological abnormalities were described as small infiltrates, usually located at the apex, 10% large infiltrates and 10% infiltrates with cavitation. Pleural abnormalities are described in 11% of cases, hilar enlargement in 4%. In subjects with active TB treated with curative chemotherapy, only 20% had large infiltrates with cavitations. Small apical infiltrates are indicative of active TB in 18% of subjects originating from Spain or Portugal, in 32% of those from Yugoslavia or Turkey, in 45% among subjects from the Middle East and 56% among Africans. Large infiltrates with cavitations are indicative of TB in 7 1 96 of subjects from Yugoslavia and 100% in Africans.
PREVALENCE
OF TB AND ETHNIC
ORIGIN
TB requiring treatment was more frequent among refugees (1.22%) than foreign workers (0.18%) and foreign students (0). The highest rate was among subjects from Africa (1.4%), Turkey (l.O%), Middle East (0.6%) and Yugoslavia (0.55%). Subjects from Eastern European countries had a prevalence of 0.19 %, from Spain and Portugal (0.14%), from other European countries (0.04%). Smear- or culture-positive cases were 0.3% among Africans and Turks (Table 2).
CLINICAL
COMPLAINTS
Only 35 % of the patients requiring treatment for TB had any complaint (cough in 63 %, weight loss in 15 %, expectorations in 13 %). About half of the patients with active disease had no complaint. Clinical examination was abnormal in only 11 patients among 132 requiring treatment. Among subjects with diagnosis other than TB, 26 % had some complaint, cough being the most frequent (50 %).
Treated
Smear- or Culturepositive
Preventive therapy
Symptoms
0 17 55
0 21 13
0 8 13
0 26 20
132
34
21
46
DISCUSSION Among 50 784 immigrants entering Vaud County, Switzerland, mass miniature X-ray screening revealed 674 abnormalities. A diagnosis of TB was made in 256 cases, of which 132 required a treatment. 34 patients were smear- or culture-positive (5 % of radiological abnormalities, 0.08 % of all immigrants). 65 % of the patients requiring treatment were asymptomatic. This had already been observed in 1956 by Calamari who stated that 75% of patients with TB discovered by mass miniature X-ray screening were asymptomatic.’ Even among patients with radiological lesions hospitalized for TB, 50 % had no symptoms.” Among immigrants, several other factors contribute to the underdeclaration of signs and symptoms of TB: lack of communication with examiners; fear of medical staff, examination or hospital services; cultural differences in the interpretation of symptoms. Among foreign workers, the fear of being rejected or refused a work permit is probably an important factor.12 The results of mass screening differed according to the groups. It was highest among refugees, lowest among foreign students, foreign workers falling in between. Considering that the prevalence of TB among immigrants reflects the prevalence in the country of origin, the differences between the groups are probably explained by the difference in origin: most of the foreign students came Table 2. Prevalence 1000 examinations Origin
of TB and X-ray abnormalities
n=
X-ray abnormalities
TB
by origin, per
Treated
Smear or culturepositive
Europe Spain and Portugal Turkey Yugoslavia Eastern countries Others Africa Asia Middle East South America Others
3 1297 1818 5629 537 6876 1141 1284 974 116 80
8.4 38.5 19 20.5 1.7 43.5 33.5 31.8 17.6
2.7 19.2 9.1 5.6 2.2 18.9 10.1 13.3 43.1
Total
50358
13.1
5
2.6
0.7
Foreign workers Refugees
43803 4512
9.1 36.3
3.6 14.6
1.8 8.4
0.5 2
1.4 10.4 5.5
0.5 3.3 0.9
1.9 0.4 14.3 2.3 6.2
3.4 2
X-ray screening for TB 325
from European countries, as did many foreign workers (with the exception of a group of workers coming from Yugoslavia, Turkey and Middle East), whereas the majority of refugees came from Third World countries with a high prevalence of tuberculosis. Therefore, the recent change in Swiss regulations stating that mass X-ray screening should be restricted to immigrants from high prevalence countries (i.e. other than the European Community. Scandinavia, Finland, North America, Australia, New Zealand) seems quite justified. Further screening of immigrants from high prevalence countries, particularly of refugees, is justified by the high yield of the examination and the fact that X-ray examination immediately discovered the potential sources of contamination before they start living within a new social group where the risk of transmission of TB can be high. Furthermore, immigrants coming from high prevalence countries have a high risk of developing TB shortly after their arrival in a new country.‘3 The early screening indicates carriers of radiological lesions and allows prescription of preventive chemotherapy to young subjects at high risk of recurrence. In low prevalence countries such as Switzerland, tuberculosis is still present in young adult immigrants and elderly residents, particularly in socially disadvantaged groups such as alcoholics, the homeless, HIVseropositives and residents of institutions for aged people.‘“” In these groups, further practice of mass screening or active search for TB can be justified, depending the local circumstances and the availability of screening services.‘7.‘X The radiological appearance of the lesions is suggestive of tuberculosis, particularly in subjects coming from high prevalence countries, but the correlation between the type of abnormality and the yield of bacteriological examination is poor.‘“.20 In Europeans, many abnormalities correspond to sequels of already treated TB whereas in Africans most of the large radiological abnormalities correspond to disease requiring treatment. For this reason, the Swiss Association against TB recently decided to change the code for interpretation of miniature X-ray, putting forward the estimated risk that an abnormality be the expression of tuberculosis without distinguishing between different radiological patterns. In view of the fact that many cases of tuberculosis among immigrants, particularly HIV-positive subjects, present with a typical radiological patterns, this seems fully justified
References 1. Clancy L, Rieder H L, Enarson D A, Spinaci S. Tuberculosis elimination in the countries of Europe and other industrialized countries. Eur Respir J 199 1;4: 1288-I 295. 2. Tala E, Liippo K. Still screening for pulmonary tuberculosis? Em Respir J 1989; 2: 397-398. 3. Horwitz 0, Darrow M M. Principles and effects of mass screening: Danish experience in tuberculosis screening. Public Health Rep 1976; 91: 146-153. 4. Toman K. Mass radiography in tuberculosis control. WHO Chronicle 1976; 30: 51-57. 5. Fairley I M, Heap B J. Pulmonary tuberculosis in Gurkhas in Hong Kong in the period 1984-1987 and the role played by routine radiology in case detection. J R Army Med Corps 1989; 135: 31-32. 6. Gordin FM, Slutkin G, Schecter G, Goodman PC, Hopewell P C. Presumptive diagnosis and treatment of pulmonary tuberculosis based on radiographic findings. Am Rev Respir Dis 1989; 139: 1090-1093. I. Association Suisse contre la Tuberculose et les Maladies Pulmonaires. Directives concernant l’utilisation de la radiophotographie pour le depistage precoce de la tuberculose. Bull OFSP 1985; Ann 4: 32-33. 8. WHO Expert Committee on Tuberculosis. WHO Technical Report, 1974; 552. 9. Association Suisse contre la Tuberculose et les Maladies Pulmonaires. Directives pour le traitement de la tuberculose. Bull OFSP 1984; Ann 4. 10. Calamari F. Aspetti della tuberculosi ignorata rivelata da11 ‘indagine schermografica. Minerva Med 1956; 47: 1238-1244. 11. Herer E, Kuaban C, Papillon F, Durieux P, Chretien J, Huchon G. Features in hospitalized patients with symptom-detected or radiologically-detected pulmonary tuberculosis. Eur Respir J 1989; 2: 3-6. 12. Ravessoud M, Zellweger J P. Clinical presentation of tuberculosis among immigrants in Switzerland. Eur Respir J I99 1; 4 (suppl 14): 496 S. 13. Nolan C M, Ehuth A M. Tuberculosis in a cohort of Southeast Asian refugees : a five-year surveillance study. Am Rev Respir Dis 1988; 137: 805-809. 14. Rieder H L, Zimmermann H, Zwahlen M, Billo N E. Epidemiologie der Tuberkulose in der Schweiz. Schweiz Rundschau Med 1990; 79: 675-679. 15. Enarson D E, Fanning E A, Allen E A. Case-finding in the elimination phase of tuberculosis: high risk groups in epidemiology and clinical practice. Bull Int Union Tuberc Lung Dis 1990; 65: 73-74. 16. Styblo K. Epidemiology of tuberculosis. Selected papers, The Royal Netherlands Tuberculosis Association 199 1; 4: I- 136. 17. Barry M A, Wall C, Shirley L, Bernard0 J, Schwingl P, Brigandi E, Lamb G A. Tuberculosis screening in Boston’s homeless shelters. Public Health Rep 1986; 101: 487494. 18. Grzyhowski S, Allen E A, Black W A et al. Inner-city survey for tuberculosis: evaluation of diagnostic methods. Am Rev Respir Dis 1987; 135: 1311-1315. 19. Hsing C T. Chest microfilm versus direct microscopic sputum examination in tuberculosis control in the developing country. Dis Chest 1967: 52: 648-65 1. 20. Gothi G D, Narayan R, Nair SS, Chakraborty A K. Srikantaramu N. Estimation of prevalence of bacillary tuberculosis on the basis of chest X-ray and/or symptomatic screening. Indian J Med Res 1976; 64: 1150-1159.
and Lung Disease (1992) 73,322-325
Mass miniature X-ray screening for tuberculosis among immigrants entering Switzerland L. Bonvin, J. P. Zellweger TB Dispensary,
University Medical Policlinic, Lausanne, Switzerland
S U M M A R Y. Among 50 784 new immigrants entering Vaud Country, Switzerland, between 1988 and 1990,
674 abnormalities were discovered by mass miniature X-ray screening on arrival (424/43803 foreign workers, 23814512 refugees and 120469 foreign students). 2043 refugees had no radiological examination. After clinical examination, tuberculosis (TB) was considered the likely diagnosis in 256 cases, of which 132 were offered an antituberculous treatment according to the current recommendations of the Swiss Association against TB. 34 of the subjects were smear- or culture-positive (5% of all radiological abnormalities, 0.08% of all immigrants). Only 46 subjects had any clinical complaint. Among foreign workers, 0.18 % were carriers of tuberculous lesions needing a treatment; the proportion was 1.22 % among refugees. By ethnic origin, the proportion is highest among Africans (1.43%), followed by Turks (1.04%), subjects from the Middle East (0.62%), Yugoslavia (0.55%), Portugal and Spain (0.14%). Mass miniature X-ray screening for TB in immigrants from high prevalence countries entering Switzerland still detects a majority of asymptomatic cases and seems an easy means of preventing the transmission of TB to members of the same community. R I? S U M .!?. Parmi 50 784 nouveaux immigrants entrant en Suisse dans le Canton de Vaud entre 1988 et
1990,674 cliches anormaux ont CtCrecenses lors d’un depistage radiophotographique (424/43 803 travailleurs &rangers, 23814512 requerants d’asile et 1212469 Ctudiants &rangers). 2043 requerants d’asile n’ont pas subi d’examen radiologique. Aprb examen clinique, 256 diagnostics de tuberculose ont CtCretenus et un traitement antituberculeux a CtC propose a 132 sujets selon les recommandations de I’Association Suisse contre la Tuberculose. 11 s’est agi 34 fois de sujets a frottis ou a culture positifs (5% de l’ensemble des anomalies radiophotographiques, 0,08% de l’ensemble des immigrants). Seuls 46 patients presentaient une anomalie clinique. Chez les travailleurs &rangers, 0,18% Ctaient porteurs d’une lesion tuberculeuse necessitant un traitement; la proportion Ctait de 1,22% chez les requerants d’asile. Selon l’origine ethnique, la proportion est la plus ClevCechez les sujets originaires de l’hfrique (1,43%), ensuite la Turquie (1,04%), le Moyen Orient (0,62%), la Yougoslavie (0,55%), le Portugal et 1’Espangne (0,14%). Le depistage antituberculeux par la radiophotographie chez de nouveaux immigrants venant en Suisse en provenance une de pays a haute prevalence de&e encore majorite des cas paucisymptomatiques, et semble un moyen simple de prevenir la transmission de la tuberculose aux membres de la m@mecommunautk. R E S U M E N. En 50 784 nuevos inmigrantes al cant&r de Vaud en Suiza entre 1988 y 1990, se detectaron
imagenes anormales en la radiofotografia miniaturizada de masa, en 674 cases (424143 803 trabajadores extranjeros, 23814512 refugiados y 1212469 estudiantes extranjeros). 2043 refugiados no tuvieron examen radiologico. DespuCs de1 examen clinico, se planted el diagnostico de tuberculosis en 256 cases y a 132 de ellos se propuso un tratamiento antituberculoso de acuerdo a las normas de Asociaci6n Suiza contra la Tuberculosis. 34 pacientes tenian baciloscopia o cultivo positivos (5 % de todos 10s cases con anormalidades radiograficas y 0,OS % de1 total de imnigrantes.) Solo 46 sujetos presentaban sintomas clinicos.
Correspondence to: L. Bonvin, TB Dispensary, University Medical Policlinic, Rue C&r-Roux 19, 1005 Lausanne, Switzerland. 322
X-my screemng for TB
323
Entre 10s trabajadores extranjeros, un 0,18 % presentaban lesiones tuberculosas que necesitaban un tratamiento; esta proporcibn era de 1,22 % entre 10s refugiados. Segtin el origen Ctnico, la proporcih m8s elevada se encontr6 en 10s africanos (1,43 %), seguida por la de Losturcos (1,04 %) 10s originarios del Medio Oriente (O&2 %), de Yugoslavia (0,55 %), de Portugal y Espafia (0,14 %). La pesquisa de tuberculosis por radiofotografia miniaturizada de masa en 10s nuevos inmigrantes que llegan a Suiza, provenientes de paises de alta prevalencia, detecta atin una mayoria de cases asintomhticos y parece ser un medio simple para prevenir la transmisih de la tuberculosis a 10s miembros de la misma comunidad.
INTRODUCTION Screening for TB in low prevalence countries means searching for asymptomatic cases within high risk groups in order to offer curative treatment to bacteriologically positive patients and preventive chemotherapy to those with a high risk of recurrence.’ Although its use in whole populations is no longer advised,‘-’ mass miniature X-ray screening can still be used for early detection of cases among high prevalence groups.’ Until 1990, mass miniature X-ray screening was compulsory for all foreign workers and foreign students entering Switzerland (in 1991 only for workers and students entering for the first time). Since 1992, the examination has been restricted to new workers and students coming from high prevalence countries, i.e. countries other than the European Community, Scandinavia, Finland, the USA, Canada, Australia and New Zealand. Until 1991, the examination was usually carried out at the border the day of entry. From 1992 it must be done in the county of settlement within 1 week after arrival, before obtaining a licence to work. Refugees (and asylum seekers) are equally submitted to mass miniature X-ray screening. Until 1991 the examination was done within the county of settlement some days or weeks after arrival. From 1992, the examinations are carried out within the first days after arrival in newly created registration centers at the border, in order to avoid delay in detection and treatment of positive cases. All the immigrants with radiological abnormalities are referred to medical centers for further examination and treatment if indicated. We retrospectively studied the result of screening among foreign workers, foreign students and refugees screened by mass miniature X-ray between 1988 and 1990 and referred for examination to the local TB Dispensary in Lausanne, Vaud county.
MATERIAL AND METHOD All foreign workers entering Vaud county in whom mass miniature X-ray screening at the border detected an abnormality were referred to the local TB Dispensary in Lausanne for further examination and treatment. Foreign students and refugees were called to an X-ray screening at the TB Dispensary where the carriers of abnormalities were immediately looked at
and treated according to the recommendations of the Swiss Association against TB. ’ Foreign workers with radiological abnormalities were not provided with a work permit before the medical examination was carried out. According to Swiss state regulations, carriers of severe abnormalities suggestive of smear-positive TB could be refused entry to Switzerland and had to return home for examination and treatment. This regulation was suppressed in 1990. Foreign students and refugees were all examined and treated in Switzerland. TB was defined as active by the association of radiological abnormalities and positive smear or culture. Cases with radiological lesions suggestive of TB but negative smear and culture and who were never or incompletely treated before were considered as inactive TB and offered preventive or curative chemotherapy according to the size of the radiological lesions, the presence or absence of suggestive symptoms and the size of the tuberculin test (in young subjects).x,y We looked retrospectively at all cases of radiological abnormalities discovered by X-ray screening and the results of the further examination at the Dispensary.
RESULTS Between January 1988 and December 1990, 50 784 immigrants entering Vaud County were submitted to mass miniature X-ray screening: 43 803 foreign workers were screened at the border, 45 12 refugees and 2469 foreign students at the local TB Dispensary. 2043 refugees had no radiological examination (pregnant women, children under 15 or subjects changing residence immediately after arrival and escaping control). Radiological abnormalities were observed in 674 subjects (1.3%): 424 foreign workers (I%), 238 refugees (5.2%) and 12 students (0.5%). After clinical and bacteriological examination a diagnosis of TB was made in 256 cases (38 % of all abnormal X-rays). Other diagnoses were pneumonia (13%) current or prior pleural disease (7%), cardiovascular abnormalities (3 %), bronchiectasis (2%), sarcdidosis (1.5%) and benign tumors (1%). Rib, chest wall and vertebral abnormalities were 9 % whereas 20 % of X-rays were considered normal after control, usually due to overestimation of non-significant abnormalities or technical defects.
324
Tubercle and Lung Disease Table 1.
Tuberculosis
among carriers of X-ray abnormalities
Abnormal X-ray
Total TB
Students Foreign workers Refugees
12 424 238
4 156 96
Total
614
256
Among the subjects with radiological lesions suggestive of TB, 34 were smear- or culture-positive for acid-fast bacilli and 132 required treatment (preventive in 21 cases, curative in 1I I) (Table 1).
RADIOLOGICAL
APPEARANCE
50% of 674 radiological abnormalities were described as small infiltrates, usually located at the apex, 10% large infiltrates and 10% infiltrates with cavitation. Pleural abnormalities are described in 11% of cases, hilar enlargement in 4%. In subjects with active TB treated with curative chemotherapy, only 20% had large infiltrates with cavitations. Small apical infiltrates are indicative of active TB in 18% of subjects originating from Spain or Portugal, in 32% of those from Yugoslavia or Turkey, in 45% among subjects from the Middle East and 56% among Africans. Large infiltrates with cavitations are indicative of TB in 7 1 96 of subjects from Yugoslavia and 100% in Africans.
PREVALENCE
OF TB AND ETHNIC
ORIGIN
TB requiring treatment was more frequent among refugees (1.22%) than foreign workers (0.18%) and foreign students (0). The highest rate was among subjects from Africa (1.4%), Turkey (l.O%), Middle East (0.6%) and Yugoslavia (0.55%). Subjects from Eastern European countries had a prevalence of 0.19 %, from Spain and Portugal (0.14%), from other European countries (0.04%). Smear- or culture-positive cases were 0.3% among Africans and Turks (Table 2).
CLINICAL
COMPLAINTS
Only 35 % of the patients requiring treatment for TB had any complaint (cough in 63 %, weight loss in 15 %, expectorations in 13 %). About half of the patients with active disease had no complaint. Clinical examination was abnormal in only 11 patients among 132 requiring treatment. Among subjects with diagnosis other than TB, 26 % had some complaint, cough being the most frequent (50 %).
Treated
Smear- or Culturepositive
Preventive therapy
Symptoms
0 17 55
0 21 13
0 8 13
0 26 20
132
34
21
46
DISCUSSION Among 50 784 immigrants entering Vaud County, Switzerland, mass miniature X-ray screening revealed 674 abnormalities. A diagnosis of TB was made in 256 cases, of which 132 required a treatment. 34 patients were smear- or culture-positive (5 % of radiological abnormalities, 0.08 % of all immigrants). 65 % of the patients requiring treatment were asymptomatic. This had already been observed in 1956 by Calamari who stated that 75% of patients with TB discovered by mass miniature X-ray screening were asymptomatic.’ Even among patients with radiological lesions hospitalized for TB, 50 % had no symptoms.” Among immigrants, several other factors contribute to the underdeclaration of signs and symptoms of TB: lack of communication with examiners; fear of medical staff, examination or hospital services; cultural differences in the interpretation of symptoms. Among foreign workers, the fear of being rejected or refused a work permit is probably an important factor.12 The results of mass screening differed according to the groups. It was highest among refugees, lowest among foreign students, foreign workers falling in between. Considering that the prevalence of TB among immigrants reflects the prevalence in the country of origin, the differences between the groups are probably explained by the difference in origin: most of the foreign students came Table 2. Prevalence 1000 examinations Origin
of TB and X-ray abnormalities
n=
X-ray abnormalities
TB
by origin, per
Treated
Smear or culturepositive
Europe Spain and Portugal Turkey Yugoslavia Eastern countries Others Africa Asia Middle East South America Others
3 1297 1818 5629 537 6876 1141 1284 974 116 80
8.4 38.5 19 20.5 1.7 43.5 33.5 31.8 17.6
2.7 19.2 9.1 5.6 2.2 18.9 10.1 13.3 43.1
Total
50358
13.1
5
2.6
0.7
Foreign workers Refugees
43803 4512
9.1 36.3
3.6 14.6
1.8 8.4
0.5 2
1.4 10.4 5.5
0.5 3.3 0.9
1.9 0.4 14.3 2.3 6.2
3.4 2
X-ray screening for TB 325
from European countries, as did many foreign workers (with the exception of a group of workers coming from Yugoslavia, Turkey and Middle East), whereas the majority of refugees came from Third World countries with a high prevalence of tuberculosis. Therefore, the recent change in Swiss regulations stating that mass X-ray screening should be restricted to immigrants from high prevalence countries (i.e. other than the European Community. Scandinavia, Finland, North America, Australia, New Zealand) seems quite justified. Further screening of immigrants from high prevalence countries, particularly of refugees, is justified by the high yield of the examination and the fact that X-ray examination immediately discovered the potential sources of contamination before they start living within a new social group where the risk of transmission of TB can be high. Furthermore, immigrants coming from high prevalence countries have a high risk of developing TB shortly after their arrival in a new country.‘3 The early screening indicates carriers of radiological lesions and allows prescription of preventive chemotherapy to young subjects at high risk of recurrence. In low prevalence countries such as Switzerland, tuberculosis is still present in young adult immigrants and elderly residents, particularly in socially disadvantaged groups such as alcoholics, the homeless, HIVseropositives and residents of institutions for aged people.‘“” In these groups, further practice of mass screening or active search for TB can be justified, depending the local circumstances and the availability of screening services.‘7.‘X The radiological appearance of the lesions is suggestive of tuberculosis, particularly in subjects coming from high prevalence countries, but the correlation between the type of abnormality and the yield of bacteriological examination is poor.‘“.20 In Europeans, many abnormalities correspond to sequels of already treated TB whereas in Africans most of the large radiological abnormalities correspond to disease requiring treatment. For this reason, the Swiss Association against TB recently decided to change the code for interpretation of miniature X-ray, putting forward the estimated risk that an abnormality be the expression of tuberculosis without distinguishing between different radiological patterns. In view of the fact that many cases of tuberculosis among immigrants, particularly HIV-positive subjects, present with a typical radiological patterns, this seems fully justified
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