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.