Sick leave due to back pain in a cohort of young workers.

PURPOSE: Evidence on risk factors for sick leave from prospective studies in work settings is limited. Furthermore, most available studies focused on workers with substantial low back disorders. These studies consistently report that physical work factors constitute a hindrance to work. However, it remains unclear whether the same risk factors are relevant in workers with less severe conditions or in early phases of the development of back pain. Therefore, this article aims to study risk factors for the occurrence of sick leave due to low back pain (LBP) among young workers with no or a modest history of back pain. METHODS: Participants were 716 young healthcare or distribution workers with no or minimal antecedents of LBP in the year before inclusion. We investigated the role of potential physical, psychosocial and individual risk factors at baseline on the occurrence of sick leave due to LBP 1 year later. To this purpose, we used Cox regression with a constant risk period. RESULTS: Six per cent (95 % CI 4.1-7.6) of the workers reported sick leave 1 year later; they accounted for 12 % of the sick-leave days independent of cause. A non-stimulating psychosocial work environment turned out to be the strongest risk factor for sick leave due to LBP (RR 6.08; 95 % CI 1.42-26.07). Physical factors were not predictive. CONCLUSIONS: In the early phases of back pain and in less severe conditions, the main benefit of interventions lies in targeting the organisation and design of jobs to create a challenging professional environment.

Genetic susceptibility in solvent induced neurobehavioral effects.

The aim of this investigation was to study the influence of genetic polymorphisms of biotransformation enzymes and dopamine receptors on neurobehavioral effects in referents (n = 53), solvent-workers (n = 144), and chronic toxic encephalopathy (CTE) patients (n = 33). All participants were interviewed for exposure data and confounding factors and underwent a clinical examination. Neurobehavioral complaints (neurotoxicity symptom checklist-60) and effects [simple reaction time (SRT), symbol digit substitution (SDS), hand-eye coordination (HEC), and digit span backwards (DSB)] were evaluated with a computer assisted test battery. The following genotypes were determined: GSTM1, GSTT1, GSTP1, DRD2 Taq1A, DRD2 Taq1B, and DRD2-141Cdel. Neurotoxic effects and complaints were significantly higher in CTE patients and were related to both duration and level of exposure. An equal distribution of genotypes was found between all groups. Logistic regression analysis revealed that GSTT1 was negatively associated with sleep and sensorimotor complaints. GSTM1 had a protecting influence on the relationship between logDSB and the cumulative exposure index and between logSRT and cumulative exposure index and degree of exposure, respectively. This effect was also found when correcting for age, education level, alcohol consumption, and smoking. DRD2-141Cdel polymorphisms had a negative influence on the relationship between logSDS and the total exposure time. GSTT1 might be protective against sleep and sensorimotor complaints, whereas GSTM1 seems to decrease sustained attention and short-term memory problems in relation to solvent exposure. Individuals possessing DRD2-141Cdel variant experienced more visuomotor problems.

The occupational risk of Helicobacter pylori infection among workers in institutions for people with intellectual disability.

OBJECTIVES: A cross-sectional study to evaluate the occupational risk for Helicobacter pylori infection, on top of other risk factors, in staff members of institutions for people with intellectual disability. In these institutions, the residents had a documented high prevalence of H pylori infection (86% presenting antibodies). As a control group, the study used administrative workers from other companies. METHODS: All participants completed a questionnaire concerning sociodemographic characteristics, medical history and employment data and they underwent a serology test. RESULTS: 671 staff members of the institutions and 439 subjects in the control group participated in the study. Prevalence of H pylori antibodies was significantly higher in the study group than in the control group (40.6% vs 29.2%; p<0.001). Crude odds ratio for occupational risk was 1.68; adjusting for the confounding effect of age, gender, body mass index, smoking, tropical journeys and number of household members during childhood resulted in an even higher (adjusted) OR of 1.98 (95% CI 1.42 to 2.69). In multiple logistic regression analysis adjusting for variables shown to be confounders, faecal contact continued to be significantly associated with H pylori infection. Attributable risk was 49.5%. CONCLUSIONS: H pylori infection is an occupational risk in healthcare workers working in institutions for people with intellectual disability. We identified faecal contact as an independent occupational risk factor for H pylori infection.

Exposure to metalworking fluids and respiratory and dermatological complaints in a secondary aluminium plant.

OBJECTIVE: Metal working fluids (MWF) are used during the machining or treatment of metal components as aluminium. The study of adverse health effects of exposure to MWF is very important because the potentially exposed population is large. In this study, we evaluated 31 workers of three departments (Extrusion, Hot and Cold Rolling Mill) in a secondary aluminium plant. METHODS: We combined exposure assessment to MWF and their biodegradation products (aldehydes, etc.) with biomonitoring 1-OH-pyrene in the urine and an evaluation of respiratory and dermatological complaints by using the Saint-George's respiratory questionnaire (SGRQ) and Dalgard's skin questionnaire. RESULTS: We only detected MWF vapour levels of 4.1 and 5.5 mg/m3 at the Cold Rolling Mills. Only very small traces of solvents, organic acids and carbon-gasses were identified in all work environments. Several aldehydes were measured in low concentrations, e.g. formaldehyde at 0.03 mg/m3. 1-OH-pyrene levels were all around the detection limit of 0.2 microg/l. The scores of the Extrusion department were all within normal values as defined in the manual of the SGRQ. In contrast, the Hot and Cold Rolling Mill were scoring significantly above the score of a population without respiratory health problems. Moreover, the participants of the Hot and Cold Rolling Mill displayed a Dalgard's Skin score = 1.3 indicating that these individuals have an increased risk of developing skin diseases CONCLUSION: We recommend measuring oil vapour, additives and contaminants in addition to oil mist only for assessing exposure to MWF. We also found indications that exposure to MWF vapours and emulsified MWF might lead to respiratory and skin problems, but a bigger epidemiological study in exposed workers will be necessary to make more definitive conclusions.

The role of physical workload and pain related fear in the development of low back pain in young workers: evidence from the BelCoBack Study; results after one year of follow up.

AIMS: To study the influence of work related physical and psychosocial factors and individual characteristics on the occurrence of low back pain among young and pain free workers. METHODS: The Belgian Cohort Back Study was designed as a prospective cohort study. The study population of this paper consisted of 716 young healthcare or distribution workers without low back pain lasting seven or more consecutive days during the year before inclusion. The median age was 26 years with an interquartile range between 24 and 29 years. At baseline, these workers filled in a questionnaire with physical exposures, work related psychosocial factors and individual characteristics. One year later, the occurrence of low back pain lasting seven or more consecutive days and some of its characteristics were registered by means of a questionnaire. To assess the respective role of predictors at baseline on the occurrence of low back pain in the following year, Cox regression with a constant risk period for all subjects was applied. RESULTS: After one year of follow up, 12.6% (95% CI 10.1 to 15.0) of the 716 workers had developed low back pain lasting seven or more consecutive days. An increased risk was observed for working with the trunk in a bent and twisted position for more than two hours a day (RR 2.2, 95% CI 1.2 to 4.1), inability to change posture regularly (RR 2.1, 95% CI 1.3 to 3.5), back complaints in the year before inclusion (RR 1.7, 95% CI 1.1 to 2.8), and high scores of pain related fear (RR 1.8, 95% CI 1.0 to 3.1). Work related psychosocial factors and physical factors during leisure time were not predictive. CONCLUSION: This study highlighted the importance of physical work factors and revealed the importance of high scores of pain related fear in the development of low back pain among young workers.

Exposure and inhalation risk assessment in an aluminium cast-house.

To date the exposure, absorption and respiratory health effects of cast-house workers have not been described since most studies performed in the aluminium industry are focused on exposure and health effects of potroom personnel. In the present study, we assessed the external exposure and the absorbed dose of metals in personnel from the aluminium cast house. This was combined with an evaluation of respiratory complaints and the lung function of the personnel. 30 workers from an aluminium casting plant participated and 17 individuals of the packaging and distribution departments were selected as controls. The exposure was assessed by the quantification of total inhalable fume with metal fraction and by the determination of urinary aluminium, chromium, beryllium, manganese and lead concentration. Carbon monoxide (CO), carbon dioxide (CO2), aldehydes and polyaromatic hydrocarbons and man-made mineral fibres concentration were assessed as well. In order to evaluate their respiratory status each participant filled out a questionnaire and their lung function was tested by forced spirometry. Total inhalable fume exposure was maximum 4.37 mg m(-3). Exposure to the combustion gases, man-made mineral fibres and metal fume was well below the exposure limits. Beryllium could not be detected in the urine. The values of aluminium, manganese and lead in the urine were all under the respective reference value. One individual had a urinary chromium excretion above the ACGIH defined biological exposure index (BEI) of 30 microg g(-1) creatinine. There was no significant difference in any of the categories of the respiratory questionnaire and in the results of the spirometry between cast house personnel and referents (Chi-square, all p > 0.05). Exposure in cast houses seem to be acceptable under these conditions. However, peak exposure to fumes cannot be excluded and the potential risk of chromium and beryllium exposure due to the recycling of aluminium requires further attention.

Hepatitis B vaccination coverage in Belgian health care workers.

BACKGROUND: The hepatitis B virus (HBV) vaccination policy for health care workers (HCW) started in Belgium in 1983. An update of vaccination coverage and rates of seroconversion and seroprotection among HCW can give an insight into the actual status and encourage further development of vaccination programs. PATIENTS AND METHODS: 5,064 HCW were tested for anti-HBs. We considered those who had a positive anti-HBs test as seroconverted (SC) and those who had an anti-HBs titer > 10 IU/l as seroprotected (SP). RESULTS: 4,771 HCW were eligible for vaccination; 84.9% of them were effectively vaccinated. Among high-risk professions (nurses, care and laboratory workers), 94.79% were vaccinated; for other professions the vaccination coverage was 69.26%. Of the 1,015 non-vaccinated persons, 293 were anti-HBs positive. Among these 54.95% declared they had had a previous hepatitis infection that was serologicaLly proven to be HBV (anti-HBc positive). Of the remaining 132 positives, 70.45% had previously undergone surgery and/or transfusion. Among these 1,015 non-vaccinated HCW, 59.03% were anti-HBs positive. Of these, 373 were nurses, care or laboratory workers. This contrasts with the results for HCW in other sectors, where 11.49% were anti-HBs positive. CONCLUSION: In our sample, high vaccination, seroconversion and seroprotection rates were achieved, at least for higher risk HCW. The same conclusion can be drawn if we consider hospital departments which carry a higher risk of blood-borne infections.

Risk factors for first-ever low back pain among workers in their first employment.

BACKGROUND: Low back pain has been estimated to be the most costly ailment of people of working age. Both work characteristics and individual factors have been identified as risk factors. The first interaction between work characteristics and individual factors occurs when workers start in their first job. AIMS: To investigate work-related risk factors for first-ever low back pain in young workers in their first employment. METHODS: A cross-sectional analysis was performed on 278 young workers in their first employment and without a history of low back pain prior to working. Work-related physical factors, psychosocial work characteristics, individual variables and first-ever low back pain were queried by means of a questionnaire. RESULTS: About half of the workers who developed low back pain after job start did so in the first year of employment. An increased risk was observed for (i) long periods of seated work [relative risk (RR) = 3.2, 95% confidence interval (CI) = 1.6-6.4]; (ii) more than 12 flexion or rotation movements of the trunk per hour (RR = 3.0, 95%CI = 1.4-6.4); and (iii) more than 3 years seniority in a job involving lifting more than 25 kg at least once an hour (RR = 3.7, 95%CI = 1.4-9.4). As to psychosocial work characteristics, first-ever low back pain was associated with a combination of low psychological job demands and low supervisor support. CONCLUSION: Work-related physical factors and psychosocial work characteristics should be considered as risk factors for first-ever low back pain. First-ever episodes of low back pain are common in the first year of employment. This may reflect a lack of work experience or training.

Analysing and interpreting routinely collected data on sharps injuries in assessing preventative actions.

BACKGROUND: Sharps injuries (SI) occur frequently in hospitals and are a risk for exposure to bloodborne pathogens. During the 1990s, the safety service of a university general hospital introduced, in collaboration with the occupational health service, specific measures to reduce the number of SI. AIM: The aim of this study was to assess the occurrence and evolution of SI during this period and to evaluate the effectiveness of the preventative measures taken, making use of routinely collected data. METHOD: In a retrospective study, we analysed the number of SI recorded from 1990 to 1997. The study population was all employees at risk of SI. Because the introduction of intensive preventative measures dates from 1996, an effect on the incidence of SI can be expected from 1996. To assess this effect, mean incidence rates for 1990-1995 and for 1996-1997 were compared. RESULTS: In the study period, a total of 4230 SI were recorded. The global SI incidence rate decreased from 33.4 SI per 100 occupied beds per year in 1990-1995 to 30.1 in 1996-1997 (P < 0.01). In the same period, among nurses a decrease in incidence rate from 17.2 to 12.7 SI per 100 person-years was noted (P < 0.0001) and for the hotel service from 4.8 to 3.7 (not significant). CONCLUSION: Although this study has various restraints, these results suggest that intensive preventative actions, in combination with technological advances, may have contributed to a drop of 67 SI cases per year.

The immunogenicity and reactogenicity profile of a candidate hepatitis B vaccine in an adult vaccine non-responder population.

Approximately 5% of vaccinees display an inadequate response after the administration of the standard three dose hepatitis B vaccine. A new hepatitis B vaccine (HBsAg/AS04) formulated with the adjuvant AS04 which contains 3'-deacylated monophosphoryl lipid A (3D-MPL) and alum has been developed. AS04 enhances the immune response which may be beneficial to non-responders. In a single-blind, randomised study, we tested the immunogenicity and reactogenicity of the new vaccine with that of commercially established hepatitis B vaccine, both on a 0, 1, 6 months schedule in 20-60 years old non-responders (titre <10 m IU/ml after four doses of hepatitis B vaccine). One month after the first dose the seroprotection rate was 44% for group 1 (58 subjects) receiving the established vaccine versus 66% for group 2 receiving HBsAg/AS04 (57 subjects) (P=0.03). One month after the second dose this was 58 and 81%, respectively (P<0.005) and 1 month after the third dose this was 68 and 98%, respectively (P<0.001). One month after each dose, GMTs were 34, 56 and 111 mIU/ml for group 1 versus 123222 and 1937 mIU/ml for the HBsAg/AS04 group (P<0.05, <0.01 and 0.0001, respectively). Pain at the injection site was the most commonly reported local symptom and very few symptoms were scored as severe. In this group of adult non-responders to previous hepatitis vaccination, the HBsAg/AS04 vaccine was well tolerated and induced, at all time-points, a superior immune response compared to the licensed hepatitis B vaccine.

Asthma prevalence in children living in villages, cities and refugee camps in Palestine.

Previous studies have suggested that asthma prevalence is generally lower in the Middle East than in more developed countries. The aim of this study was to investigate the prevalence and severity of asthma and asthma symptoms in schoolchildren in the Ramallah District in Palestine. In the autumn of 2000, 3,382 schoolchildren aged 6-12 yrs were surveyed in 12 schools, using the International Study for Asthma and Allergies in Childhood (ISAAC)-phase III, parents-administered translated questionnaire. The crude prevalence rates for "wheezing-ever", "wheezing in the previous 12 months", and "physician-diagnosed asthma" were 17.1, 8.8 and 9.4% respectively, with urban areas having higher prevalence rates than rural areas. Within urban areas, refugee camps had higher prevalence rates than cities. Yet, within the rural areas, the 12-month prevalence was lower in the deprived villages than other residences. Place of residence remained significant for asthma and asthma symptoms, after adjusting for sex, age, and place of birth. To conclude, children from refugee camps appear to be at higher risk of asthma than children from neighbouring villages or cities. The prevalence of asthma and asthma symptoms in Palestine appears to be close to that of Jordan, but it is much lower than Israel, and lower than some other countries in the region, such as Kuwait and Saudi Arabia, and more developed countries. This initial study is a baseline for a study on lifestyle and environmental determinants for asthma among Palestinian children.

Psychometric properties of the "Modified Transplant Symptom Occurrence and Symptom Distress Scale".

The aim of this study was to assess key aspects of the reliability and validity of the "Modified Transplant Symptom Occurrence and Distress Scale," an instrument measuring symptom experience associated with side effects of triple drug therapy in transplant patients. This cross-sectional, comparative study included 108 renal transplant recipients (61% men; 39% women) with a median age of 47 years and a median posttransplant status of 5.5 years. Renal transplant patients were matched by age and gender with 108 healthy control persons not taking immunosuppressive drugs. Content validity, construct validity and discriminant validity of the instrument were substantiated. Internal consistency reliability was not useful to assess in this instrument, as the conditions for calculating Cronbach's alpha were not satisfied. These findings document the validity of the "Modified Transplant Symptom Occurrence and Symptom Distress Scale" as an instrument to measure symptom experience with immunosuppressive drugs.

Observer variation in computed tomography of pleural lesions in subjects exposed to indoor asbestos.

To assess the reliability of computed tomography (CT) in detecting discrete pleural lesions, the interobserver and intra-observer variability in reading the conventional and high-resolution CT (HRCT) scans of 100 volunteers, who had worked for > or = 10 yrs in a building with known asbestos contamination, was evaluated. In the first session, pleural abnormalities were detected by a single radiologist (A1) in 13 subjects. In the second session, the scans were read again independently by the same radiologist (A2) and two other experienced radiologists (B, C). The final decision for the presence of pleural lesions was made in a final consensus reading. This gave a diagnosis of pleural abnormalities in 18 subjects, of whom eight (44%) had been detected by all three readers, five (28%) by two readers and four (22%) by only one reader; one scan, rated normal by all readers during the second session, was reconsidered because pleural abnormalities had been noted at the first reading (A1). The intra-observer agreement for reader A was good (kappa (kappa) 0.68) but the interobserver agreement between the readers was only fair to moderate (weighted kappa: A2-B=0.43, A2-C = 0.45, B-C = 0.26) in the second reading session. In conclusion, when looking for the prevalence of pleural lesions in indoor asbestos exposed subjects, the potential lack of consistency in reporting the presence of small pleural abnormalities must be borne in mind and strict precautions must be taken.

Occupational risk of infection by varicella zoster virus in Belgian healthcare workers: a seroprevalence study.

OBJECTIVES: To assess the prevalence of varicella zoster virus (VZV) antibodies in Flemish (Belgian) healthcare workers, to investigate the association between seronegativity and selected variables, and to assess the reliability of recall about disease as a predictor of immunity. METHODS: A seroprevalence study of VZV antibodies (IgG) was conducted among a systematic sample of 4923 employees in various professional groups, employed in 22 hospitals in Flanders and Brussels (Belgium). Information about sex, age, department, job, and years of employment, the country of origin, and history of varicella was obtained. The presence of VZV antibodies was investigated with the enzyme linked immunosorbent assay (ELISA), Enzygnost anti VZV / IgG (Dade Behring, Marburg, Germany). Statistical analysis was performed by calculating prevalences and prevalence ratios (PRs) and their 95% confidence intervals (95% CIs). Sensitivity, specificity, and positive and negative predictive values (PPV and NPV) of the recalled history were determined. RESULTS: The prevalence of VZV seropositivity in Flemish healthcare workers was 98.5% (95% CI 98.1 to 98.8). Seronegativity was significantly associated with age and job, increasing with both older and younger age. The prevalence of seronegative workers was significantly less in nursing staff than non-nursing staff. There was no significant difference for sex and years of employment. The PPV and NPV of recalled history were 98.9% and 3.4%. Sensitivity and specificity were 83% and 38.9%. CONCLUSION: The prevalence of VZV seropositivity was very high in this sample of Flemish healthcare workers. Because of this low overall susceptibility, VZV infection seems not to be an important occupational risk among healthcare workers in Flanders. The increasing seronegativity above the age of 45 is possibly due to a loss of detectable antibodies. A positive history of varicella was a good predictor of immunity, but a negative history had no value as a predictor of susceptibility in adults.

Prevalence of hepatitis C antibodies in a large sample of Belgian healthcare workers.

OBJECTIVE: To assess the risk of hepatitis C virus (HCV) infection among Belgian (Flemish) healthcare workers. DESIGN: A seroprevalence survey of HCV IgG antibodies. SETTING AND PARTICIPANTS: A systematic sample of 5,064 employees from 22 general hospitals in Flanders and Brussels, Belgium, was tested at the annual occupational medical examination. Together with demographic and occupational data, information was collected on the frequency of blood contact, needlestick injuries, and medical and surgical history. The blood samples were tested using the third-generation Abbott Screen Kit test, with confirmation by Matrix, LIA, and an in-house polymerase chain reaction and the Quantiplex-HCV b-DNA test. RESULTS: 21 persons were found to be positive for HCV markers. The overall prevalence was 0.41% (95% confidence interval [CI95], 0.24-0.59). A statistically significant association was found with a history of blood transfusion (odds ratio [OR], 4.14; CI95, 1.67-10.31) and with history of a clinically apparent hepatitis (OR, 3.98; CI95, 1.60-9.90). Although the ORs for the frequency of blood contact were slightly elevated (between 1.17 and 2.73), this association was not significant. Moreover, a history of needlestick injuries showed a nonsignificant OR of 1.28 (CI95, 0.53-3.09), and no statistically significant difference was found with a variety of duties and tasks. The ORs for potential occupational risk factors were adjusted according to age, gender, antecedents, and other confounders using a logistic regression analysis. Based on this procedure, the ORs decreased slightly. CONCLUSIONS: Flemish healthcare workers showed a lower HCV seropositivity than is seen in the general population; a history of blood transfusion and of clinically apparent hepatitis was most strongly associated with the presence of HCV markers. We concluded that employees in Flemish regional general hospitals are not at an overall increased risk for HCV infection, although occasional transmission through percutaneous injuries is possible, and prevention therefore remains imperative.

Nuclear 24 kD fibroblast growth factor (FGF)-2 confers metastatic properties on rat bladder carcinoma cells.

The tumorigenic and metastatic properties of rat bladder carcinoma NBT-II cells transfected with a cDNA encoding the 24 kD nuclear isoform of human fibroblast growth factor-2 (FGF-2) were analysed and compared with those cells producing the 18 kD cytoplasmic isoform FGF-2. In transfected clones, 24 kD FGF-2 was found in the nucleus, and no FGF-2 was secreted. RT-PCR analysis showed no upregulation of FGF-2-specific receptor FGFR2c expression in these proliferating transfected cells. A shorter latency period for in vivo tumor formation and abundant spontaneous lung metastases were only seen if nuclear FGF-2-producing cells were injected subcutaneously into nude mice. Intravenous injection of 24 kD FGF-2-producing cells led to extensive experimental lung metastases whereas injection of control NBT-II cells or 18 kD FGF-2-producing cells did not. As FGF-2-producing cells have no specific FGF-2 receptors, our results suggest that the 24 kD FGF-2 has nuclear targets, and activates metastatic property of carcinoma cells via a mechanism other than the conventional FGF receptor-mediated signaling pathway.

The SFL activity secreted by metastatic carcinoma cells is related to laminin 5 and mediates cell scattering in an integrin-independent manner.

We have previously reported that an in vivo-selected metastatic variant of NBT-II rat carcinoma cells, M-NBT-II, produces and secretes a factor with cell-scattering activity, SFL, that is potentially involved in tumor progression. This biological activity was purified and characterized as a laminin 5 (LN5) -related protein. This SFL/LN5 protein consists of the (alpha)3, (beta)3 and (gamma)2 chains of expected sizes. Laminin 5 is a multifunctional secreted glycoprotein thought to be involved in cell adhesion and migration, mainly via its interaction with (alpha)3(beta)1 and (alpha)6(beta)4 integrins. SFL/LN5, and purified human laminin 5, induced the scattering and motility of MDCK cells and the formation of actin stress fibers and focal contacts in A549 cells. These events were dependent on activation of the small GTP-binding protein Rho. (Alpha)v colocalized with vinculin in the focal contacts of activated cells whereas (alpha)3 and (alpha)6 integrins did not. Blocking antibodies directed against (alpha)3 and (alpha)6 integrins or the laminin 5 integrin-binding site did not abolish SFL/LN5 biological activity, which, in contrast, was completely inhibited by heparin. Thus, SFL/LN5 activity in epithelial cell scattering and cytoskeletal reorganization is probably independent of integrin receptors.

The community effect in FGF-1 mediated tumor progression of a rat bladder carcinoma does not involve a direct paracrine signaling.

A community effect was found to occur between heterogeneous tumor cell populations leading to an overall increased tumorigenicity without a clonal dominance of the more tumorigenic clone. In the rat bladder carcinoma cell line NBT-II, this effect appears mediated by the Fibroblast Growth Factor-1 (FGF-1) through either a direct or an indirect signaling pathway. Neovascularization induced by FGF-1 was found not to be responsible for the community effect. The present study shows that the community effect does not involve a direct FGF-1 signaling since tumor cells expressing a dominant-negative FGF receptor mutant were still responding to the highly tumorigenic FGF-1 expressing cells. Tumors arising from inoculates of the FGF-1 producing NBT-II cells mixed with non tumorigenic epithelial MDCK cells contain only the tumorigenic cells indicating that MDCK cells may exerce a helper effect for the growth of the tumor not dependant on their own growth. Therefore the helper function of MDCK cells must be distinguished from a community effect where the contribution of low tumorigenic cells not only provides an in vivo growth advantage to few highly tumorigenic cells but become themselves highly tumorigenic indicating that the community effect may require cell-cell specific cooperativity independent from an helper effect.

Prevalence of hepatitis A antibodies in a large sample of Belgian health care workers.

Health care workers (HCW), especially women (for example, pediatric nurses and day nursery workers), have been shown to be at risk for viral hepatitis A infections. In order to obtain a more precise estimate of the risk in Belgian HCW, a seroprevalence study was undertaken. The data from this study have been compared with the age-specific seroprevalence of anti-HAV in the general population (GP) as recently estimated. During 1996-1997, a sample of 5,068 employees in 22 general hospitals, geographically distributed over the Flemish and Brussels regions of Belgium, was tested for the presence of anti-HAV. Comparison of the anti-HAV prevalences in HCW and GP shows a significantly lower prevalence in HCW for the age groups 25-34, 35-44 and 45-54 years. Within these age-groups, employees performing catering tasks have the highest prevalence. This difference could be explained by socioeconomic parameters: overrepresentation of higher social classes in better educated HCW. The number of unprotected individuals in young and older age groups (25-54 years) is greater than in the general population. In view of the changing HAV epidemiology in western Europe, the number of unprotected persons will rise in the coming years. Considering the more severe course of the disease as age increases, vaccination may become important in the occupational health strategy for HCW.