A total of 20 314 individuals were mailed an invitation to participate. Of those mailed, 8515 (42%) agreed to participate. Of those who participated, there were 7550 (89%) with blood specimens available for serological testing. An overview of the number of participants in the study is shown in fig 1. There were a total of 7527 participants not previously diagnosed with coeliac disease included in the analyses. Mean age of these participants was 59 years (SD 8.9) and 4444 (59%) were female. Of the 7440 EMA negative participants, nine had evidence of selective IgA deficiency. Estimates of the seroprevalence of undetected coeliac disease are shown in table 1. The overall seroprevalence of undetected coeliac disease was 1.2% (95% confidence interval (CI) 0.9–1.4) based on EMA positivity alone (n=87) and 1.0% (95% CI 0.8–1.3) based on EMA positive and abnormal tTGA results (n=77). Seroprevalence showed little variation with age or sex. Table 2 shows the distribution of tTGA results in EMA positive participants considered to have undetected coeliac disease. In 75% of EMA positive participants, tTGA results were unequivocally abnormal (>6 U/ml). EMA positive participants were less likely to have reported being ex or current smokers (table 3) compared with EMA negative participants, and also showed a trend towards higher social class, although this was not significant at the 5% level (χ2 for trend, p=0.08). Mutual adjustment and adjusting for age and sex did not appreciably change these associations.
Seroprevalence of undetected coeliac disease using antiendomysial antibody (EMA) and human antitissue transglutaminase (tTGA) tests by age and sex
tTGA results in EMA positive participants considered to have undetected coeliac disease
Sociodemographic and smoking characteristics of study participants by antiendomysial antibody (EMA) result
In univariate analyses, EMA positive participants had lower mean haemoglobin, total protein, corrected calcium, cholesterol, low density lipoprotein, triglyceride, diastolic blood pressure, and weight (all p<0.05) (table 4). Mean body mass index (BMI), hip and spine BMD, systolic blood pressure, mean cell volume, and albumin were all slightly lower in participants with undetected coeliac disease but these differences were not significant at the 5% level. Both alanine aminotransferase and platelet count were higher among EMA positive participants. After adjustment for age, sex, smoking status, and social class, differences in weight and diastolic blood pressure were not significant at the 5% level.
Distribution of selected physiological variables by antiendomysial antibody (EMA) test result
In the multivariate analyses, undetected coeliac disease was associated with a reduction of 0.5 mmol/l (95% CI 0.3–0.8) in cholesterol and 0.3 g/dl (95% CI 0.1–0.5) in haemoglobin. For BMD, the mean difference at the hip was −0.02 g/cm2 (95% CI −0.05 to +0.02) and at the spine 0.03 g/cm2 (95% CI −0.07 to +0.02). There were significant interactions between the effects of EMA result and sex on corrected calcium (p=0.001). Mean corrected calcium was reduced in EMA positive participants among women only (−0.05 mmol/l (95% CI −0.07 to −0.02)).
There were no statistically significant associations between undetected coeliac disease and reported morbidity but having high blood pressure, high cholesterol, angina or a heart attack, diabetes, or bronchitis/emphysema all appeared to be less common in those who were EMA positive (table 5). In 75 of 85 (88%) EMA positive participants and 5527 of 7015 (79%) EMA negative participants, general health was reported as “good or excellent”, giving an odds ratio of 1.76 (95% CI 0.90–3.46) adjusted for age, sex, social class, and smoking status. There was no difference in the proportion of deaths recorded (EMA negative 591 (7.9%); EMA positive 5 (5.7%); χ2 p=0.6). Underlying causes of death given for the five EMA positive participants were carcinoma of the pancreas, acute myeloid leukaemia, ischaemic heart disease, carcinoma of the cervix, and B cell lymphoma (not otherwise specified).
Relation between participants with positive antiendomysial antibody (EMA) test result and reported morbidity
Fourteen of 87 (16.1%) EMA positive participants and 315 of 7425 (4.2%) EMA negative participants were found to be anaemic, giving an odds ratio of 4.56 (95% CI 2.53–8.21) adjusted for age, smoking status, sex, and social class. Of the EMA positive anaemic participants, nine were women (haemoglobin range 10.1–11.3 g/dl) and five were men (haemoglobin range 11.6–12.8 g/dl). In seven of 58 (12.1%) EMA positive participants and 311 of 5024 (6.2%) EMA negative participants, BMD at the hip showed osteoporosis, giving an odds ratio of 3.08 (95% CI 1.31–7.25) adjusted for age, BMI, smoking status, and social class.