Objective: To investigate whether the increased chances of having a diagnosis of irritable bowel syndrome (IBS) and pelvic inflammatory disease (PID) in women with endometriosis is due to misdiagnosis or co-morbidity.
Design: A case-control study of women aged 15-55 years with endometriosis and matched controls.
Setting: Data from the UK's General Practice Research Database for the years 1992-2001.
Sample: A total of 5540 women aged 15-55 years, diagnosed with endometriosis, each matched to four controls without endometriosis. The index date was defined as the date of diagnosis.
Methods: Data were analysed to determine whether women with endometriosis were more likely to receive a diagnosis of PIDor IBS than women without endometriosis. Odds ratios were calculated for endometriosis associated with IBS and PID before and after the index date.
Main outcome measures: Diagnosis of IBS or PID before and after the index date.
Results: Compared with the controls, women with endometriosis were 3.5 times more likely to have received a diagnosis of IBS (OR 3.5 [95% CI: 3.1-3.9]). Even after women had been diagnosed with endometriosis, they were still two and a half times more likely to receive a new diagnosis of IBS when compared with the controls (OR 2.5 [95% CI: 2.2-2.8]). Similarly, women with endometriosis were more likely than those without endometriosis to have been treated for PID both before (OR 5.9 [95% CI: 5.1-6.9]) and after (OR 3.8 [95% CI: 3.1-4.6]) being diagnosed with endometriosis.
Conclusions: Women with endometriosis are more likely to be diagnosed with IBS and PID than controls, even after a definitive diagnosis of endometriosis has been reached.