Table 1.
Main characteristics of the studies included in this meta-analysis.
| Loftus et al.16 | van Erpecum et al.19 | Mitchell et al.18 | Andersen et al.13 | |
|---|---|---|---|---|
| Country | USA | The Netherlands | England | Norway |
| Study design | Case-control study | Case-control study | Case-control study | Case-control study |
| Year | 1996 | 1996 | 2002 | 2014 |
| Total number | 70 (35 cases with PSC and 35 controls without PSC) | 256 (59 cases with PSC and 197 controls without PSC) | 211 (41 cases with PSC and 170 controls without PSC) | 485 (240 cases with PSC and 245 controls without PSC) |
| Study sample | Cases: Cases were patients with PSC who were seen at Mayo Clinic, Minnesota, from January 1984 to December 1988 Controls: Controls were patients without PSC who were seen at Mayo Clinic, Minnesota, at the same period of time. Controls were sex-, age-, and geography-matched to cases. | Cases: Cases were patients with PSC who were seen at the University Hospitals Utrecht and Rotterdam from November 1994 to April 1995. Controls: Controls were patients without PSC who were seen at neurologic or orthopedic clinics of the University Hospital Utrecht from January 1995 to April 1995. | Cases: Cases were (a) patients with PSC who were seen at the liver and IBD clinics, (b) patients with PSC in the PSC database at the Oxford Radcliffe Hospital, and (c) patients with PSC from the National PSC Patient Group. Controls: Controls were patients without PSC who shared the same primary physicians with their corresponding cases. Controls were also sex- and age-matched to cases. | Cases: Cases were patients with PSC who were seen at Oslo University Hospital Rikshospitalet from 1992 to 2011. Controls: Controls without PSC were randomly chosen from the Norwegian Bone Marrow Donor Registry. Controls were sex- and age-matched to cases. |
| Determination of smoking status | Health questionnaires | Health questionnaires | Health questionnaires | Health questionnaires |
| Diagnosis of PSC | ERCP or MRCP and/or liver biopsy | ERCP or MRCP and/or liver biopsy | ERCP or MRCP and/or liver biopsy | ERCP or MRCP and/or liver biopsy |
| Confounder adjusted in multivariate analysis | Age | Sex, age, and history of previous appendectomy | None | Age, sex, and education level |
| Quality assessment (Newcastle-Ottawa scale) | Selection: 3 Comparability: 2 Exposure: 2 | Selection: 3 Comparability: 1 Exposure: 3 | Selection: 4 Comparability: 2 Exposure: 3 | Selection: 4 Comparability: 2 Exposure: 3 |
PSC: primary sclerosing cholangitis; ERCP: endoscopic retrograde cholangiopancreatography; IBD: inflammatory bowel disease; GGT: gamma-glutamyltransferase; MRCP: magnetic resonance cholangiopancreatography; USA: United States of America.