A clinical score can predict associated deep infiltrating endometriosis before surgery for an endometrioma.

STUDY QUESTION

Is it possible to detect associated deep infiltrating endometriosis (DIE) before surgery for patients operated on for endometriomas using a preoperative clinical symptoms questionnaire?

SUMMARY ANSWER

A diagnostic score of DIE associated with endometriomas using four clinical symptoms defined a high-risk group where the probability of DIE was 88% and a low-risk group with a 10% probability of DIE.

WHAT IS KNOWN ALREADY

Many clinical symptoms are already known to be associated with DIE but they have not yet been used to build a clinical prediction model.

STUDY DESIGN, SIZE, DURATION: We built a diagnostic score of DIE based on a case control study of 326 consecutive patients operated on for an endometrioma between January 2005 and October 2011: 164 had associated DIE (DIE+) and 162 had no DIE (DIE-). We derived the score on a training sample obtained from a random selection of 2/3 of the population (211 patients, 101 DIE+, 110 DIE-), and validated the results on the remaining third (115 patients, 63 DIE+, 52 DIE-). The gold standard for the diagnosis of DIE was based on surgical exploration and histological diagnosis.

PARTICIPANTS/MATERIALS, SETTING, METHODS: Participants were consecutive patients aged 18-42 years who underwent surgery for an endometrioma with histological confirmation and complete treatment of their endometriotic lesions: data for these women were extracted from a prospective database including a standardized preoperative questionnaire. On the training dataset, variables associated with DIE in a univariate analysis were introduced in a multiple logistic regression and selected by a backward stepwise procedure and a Jackknife procedure. A diagnostic score of DIE was built with the scaled/rounded coefficients of the multiple regression. Two cut-off values delimitated a high and a low risk group, and their diagnostic accuracy was tested on the validation dataset.

MAIN RESULTS AND THE ROLE OF CHANCE

Four variables were independently associated with DIE: visual analogue scale of gastro-intestinal symptoms ≥5 or of deep dyspareunia >5 (adjusted diagnostic odds ratio (aDOR) = 6.0, 95% confidence interval (CI) [2.9-12.1]), duration of pain greater than 24 months (aDOR = 3.8, 95% CI [1.9-7.7]), severe dysmenorrhoea (defined as the prescription of the oral contraceptive pill for the treatment of a primary dysmenorrhoea or the worsening of a secondary dysmenorrhoea) (aDOR = 3.8, 95% CI [1.9-7.6]) and primary or secondary infertility (aDOR = 2.5, 95% CI [1.2-4.9]). The sum of these variables weighted by their rounded/scaled coefficients constituted the score ranging from 0 to 53. A score <13 defined a low-risk group where the probability of DIE was 10% (95% CI [7-15] with a sensitivity of 95% (95% CI [89-98]) and a negative likelihood ratio of 0.1 (95% CI [0.0-0.3]). A score ≥35 defined a high-risk group where the probability of DIE was 88% (95% CI [83-92%]), with a specificity of 94% (95% CI [87-97]), and a positive likelihood ratio of 8.1 (95% CI [3.9-17.0]). The performance of the score was confirmed on the validation dataset with 11% of DIE+ patients having a score <13 (sensibility: 95%) and 90% of DIE+ patients having a score ≥35 (specificity: 94%).

LIMITATION, REASONS FOR CAUTION: This study was performed in a department specialized in DIE management. Score accuracy could be different in less specialized centres.

WIDER IMPLICATIONS OF THE FINDINGS

This score could have a major clinical impact on the time of diagnosis, the management of DIE and could reduce the cost of investigations by helping to identify high-risk patients, while preserving the quality of care.

STUDY FUNDING/COMPETING INTERESTS: The authors have no competing interests to declare. No grant supported the study.