Twenty-four studies with a total of 36,302 patients: 14 studies based in the general population (n=31,993), and 10 hospital-based studies (n=4,309). Of the hospital-based studies, 4 selected patients with 'mild disease' and 6 selected patients with 'serious disease'.
Over 13% (4,891 out of 36,302) of the patients had gallstones. The prevalence of gallstones depended on the setting of the study: the prevalence was 12.4% (3,967 out of 31,993) in the general population, and 21% (924 out of 4,309) in a referred (to hospital) population. In both settings, the prevalence varied widely between studies (5 to 35% and 11 to 50%, respectively).
The positive and negative predictive values, respectively, for each symptom in the general population were: 23 and 90 for upper abdominal pain; 17 and 92 for biliary colic; 10 and 93 for radiating pain; 24 and 89 for the use of analgesics; 9 and 92 for food intolerance; and 16 and 86 for fat intolerance.
The positive and negative predictive values, respectively, for each symptom in the referred population (hospital-based) were: 30 and 79 for upper abdominal pain; 50 and 81 for biliary colic; 38 and 81 for radiating pain; 50 and 81 for the use of analgesics; 40 and 73 for tenderness of the upper abdomen; 23 and 82 for food intolerance; and 30 and 79 for fat intolerance.
The unadjusted pooled DORs for all the symptoms studied were low. The DOR was 1.7 (95% CI: 1.5, 2.0) for upper abdominal pain (13 studies); 2.6 (95% CI: 2.4, 2.9) for biliary colic (9 studies); 2.8 (95% CI: 2.2, 3.7) for radiating pain (5 studies); 2 (95% CI: 1.6, 2.5) for the use of analgesics (4 studies); 1.8 (95% CI: 1.3, 2.4) for tenderness of the upper abdomen (3 studies); 1.3 (95% CI: 1.1, 1.6) for food intolerance (6 studies); and 1.3 (95% CI: 1.1, 1.5) for fat intolerance (11 studies).
The chi-squared test statistic showed that both the true positive rates and false positive rates were heterogeneous for all the symptoms studied (P<0.001). For the symptoms abdominal pain, biliary colic and the use of analgesics, logistic regression showed a statistically significantly different diagnostic accuracy for the different clinical settings. Different spectra of the disease showed a statistically significantly different discriminative capacity in the symptoms abdominal pain, biliary colic, and food intolerance.
Neither the gender of the studied population, the blinding of the reader to the reference standard, or the reference standard used, could explain the heterogeneity in the results. The lack of control for confounding age in most studies precluded the evaluation of age as an explanation for the discrepancies in the results.
The symptoms biliary colic, radiating pain and analgesics used were consistently related to gallstones. The DOR of biliary colic increased with the extent of gallstone disease: the DOR was 3.5 (95% CI: 2.3, 5.3) for 'mild disease' and 13.3 (95% CI: 4.2, 42) for 'serious disease'.
The methodological quality of most of the included studies was low. Only eight studies blinded the reader to the reference standard for the abdominal symptoms of the patients; only eight studies controlled for both age and gender; and in the hospital-based studies, the extent of gallstone disease in the included patients was barely described.