Mortality in cases of asbestosis diagnosed by a pneumoconiosis medical panel.

One hundred and fifty five male cases of asbestosis certified by the London Pneumoconiosis Medical Panel during 1968-74 were followed up during 1978-9, 4-11 (mean 7.5) years after certification. Fifty nine patients had died, 23 (39%) from lung cancer, 6 (10%) from mesothelioma, and 11 (19%) from other respiratory causes. The number of observed deaths was 2.25 times greater than expected and 7.4 times greater than expected for lung cancer. Adenocarcinoma was the commonest histological type but other cell types were also increased. Finger clubbing (p less than 0.01) and percentage of predicted FEV1 (p less than 0.01) were of value in predicting death, but increasing profusion of small opacities greater than 1/0 (ILO/U-C international classification of radiographs of pneumoconiosis, 1971), duration of exposure to asbestos, time from first exposure to asbestos, and percentage of predicted vital capacity and transfer factor did not predict death.

Significance of finger clubbing in asbestosis.

The prognostic significance of finger clubbing in asbestosis has been assessed in 167 cases certified by the London Pneumoconiosis Medical Panel from 1968 to 1974. Finger clubbing developed early in the clinical course of the disease and was associated with a lower gas transfer, a higher mortality and a greater likelihood of progression in intrapulmonary fibrosis than was found among cases without finger clubbing. Finger clubbing was not associated with heavier asbestos exposure. Its presence appears to be associated with a more severe form of disease.

Histocompatibility antigens in coal miners with pneumoconiosis.

Twenty-five histocompatibility antigens have been measured in 100 coal miners with pneumoconiosis attending a pneumoconiosis medical panel and the results compared with a panel of 200 normal volunteers not exposed to dust. Chest radiographs were read independently by three readers according to the ILO U/C classification. On a combined score, 40 men were thought to have simple pneumoconiosis and 60 men complicated pneumoconiosis. The number of antigens tested and associations between antigens caused difficulties in assessing the statistical significance of differences in prevalence of antigens between groups of men. Using stringent criteria for statistical significance, no significant differences were found in antigen prevalences between miners and controls, or miners with simple or complicated pneumoconiosis. When a less stringent statistical approach was applied, three antigens appeared to have abnormal prevalences in these 100 miners by comparison with the normal volunteers. More detailed examination of these antigen prevalences in relation to radiographic category of pneumoconiosis did not provide any supportive evidence that these slight associations were of statistical or clinical significance. Reports on histocompatibility antigens in miners with pneumoconiosis are reviewed briefly and the results compared. There is no good evidence that any of the histocompatibility antigens so far tested are associated with a clinically important altered risk of simple or complicated pneumoconiosis when dust is inhaled.

The role of histocompatibility (HLA) antigens in asbestosis.

Histocompatibility antigens on the A, B and C loci have been studied in 172 asbestos workers, 92 of whom had radiographic evidence of asbestosis and 80 of whom had normal radiographs. Within each population, 77 were selected who matched for age, sex, duration from first exposure, duration of exposure and approximate heaviness of exposure. Results were also compared with 174 normal unexposed volunteers. No differences of statistical significance were found in the frequency of histocompatibility antigens tested when the matched or the total population of asbestos workers with and without asbestosis were compared. There was, however, a consistent trend of increase in B27 amongst those with asbestosis (11%) and this reached conventional significance (P < 0.05) when the 92 asbestotics were compared with the whole group having normal radiographs (asbestos workers 5.0% and volunteers 5.2%). Amongst the group having asbestosis, those with HLA-B27 had a significantly shorter exposure to the dust (13.5 years) compared with those without asbestosis (22.3 years), although the mean radiographic profusion score for the two categories was similar. No statistical differences could be found when B5, B8 and B12 were analysed in a similar way, but there was a trend suggesting that B5 was less frequent amongst a small group of cases showing radiographic progression over a three-year follow-up, compatible with the suggestion that this antigen might be linked with with some protective effect.

The HL-A system in asbestos workers.

In a study of the HL-A system in 56 selected asbestos workers referred to the Pneumoconiosis Medical Panel with definite or suspected asbestosis, the W 27 antigen was found more often than among a control population. Six of the 10 asbestos workers with the W 27 antigen had definite radiographic evidence of asbestosis compared to 13 out of 46 without the W 27 antigen. These observations, if confirmed, suggest that the W 27 antigen may provide a useful marker of an enhanced susceptibility to the tissue-damaging effects of asbestos dust.

Circulating antinuclear antibody and rheumatoid factor in coal pneumoconiosis.

Circulating antinuclear antibody and rheumatoid factor have been measured in 109 coal miners with pneumoconiosis whose chest radiograph showed a range of abnormalities varying from simple pneumoconiosis of mild degree to advanced progressive massive fibrosis.At a screening dilution of 1/10 the overall incidence of antinuclear antibody was 17%. In almost half of the positive cases the titre was 1/40 or greater.The prevalence of antinuclear antibody was lowest in those with simple pneumoconiosis (9%) and highest in those with category C progressive massive fibrosis (27%). A similar but less striking trend was seen with rheumatoid factor, ranging from 6% in simple pneumoconiosis to 18% in category C progressive massive fibrosis. The trend of increasing frequency of autoantibodies with advancing radiographic category was most marked when the frequencies of antinuclear antibody and rheumatoid factor were combined. These autoantibodies were found in 13% of the miners with simple pneumoconiosis and 45% of those with category C progressive massive fibrosis (P for the trend=0.01).

Circulating rheumatoid and antinuclear factors in asbestos workers.

In an unselected series of 80 patients with asbestos exposure referred to the London Pneumoconiosis Medical Panel, antinuclear and rheumatoid factors were found in 28 and 27% respectively. This probably represents at least a fourfold increase over their incidence in random populations. The presence of these autoantibodies was not related to the duration of exposure, but was related to the extent of radiographic abnormality.