Review question
Is three-dimensional saline infusion sonography (3D SIS) better than two-dimensional (2D) SIS for detecting polyps and fibroids?
Background
The womb (uterus) is one of the female reproductive organs. Inside the cavity of the womb, abnormalities such as polyps and fibroids can grow. Polyps and fibroids can cause problems such as abnormal menstrual bleeding and difficulty getting pregnant. The presence of these polyps and fibroids may be a reason for clinicians to start drug therapy or remove the polyps and fibroids during surgery.
Ultrasonography can provide a picture of the womb and of possible fibroids or polyps. Saline or gel inside the cavity of the womb makes the ultrasound image more clear. This technique is called saline infusion sonography (SIS). Usually, this picture is only two-dimensional. Nowadays, it is possible to make a three-dimensional picture so the type of abnormality can be better seen.
Study characteristics
Review authors searched for studies published from inception until March 2016 and found 13 studies (in total 1053 women), eight of which directly compared 3D SIS versus 2D SIS. Data included all women reporting abnormal menstrual bleeding or difficulty getting pregnant. The number of patients in these studies varied from 23 to 180 women.
Quality of the evidence
In all studies, researchers checked the results of 2D SIS and 3D SIS against results obtained when a camera was used to look inside the womb (hysteroscopy); this is expected to give the true picture but is also more painful for the patient. All studies were performed in the usual way. Some studies did not report several items that might have influenced the results. For example, not all studies made it clear that the person evaluating the ultrasound pictures was unaware of the hysteroscopy results, and vice versa. The main problem involving the quality of included studies is insufficient reporting of study methods, resulting in unclear risk of bias for several of the quality domains assessed. Therefore, review authors considered the overall quality of the evidence as low.
Key results
Low-quality evidence suggests that 3D SIS may be very accurate in detecting polyps and fibroids. Our analysis revealed no clear differences between 2D SIS and 3D SIS. Summary results are higher for 3D SIS but margins of improvement are limited because 2D SIS is already very accurate. Results show that 2D SIS missed a fibroid or polyp in 9 of 100 women and 3D SIS missed a polyp or fibroid in 3 of 100 women who had them. In 4 of 100 women, 2D SIS indicated the presence of polyps or fibroids when there were none, and in less than 1 in 100 women, 3D SIS was wrong. In theory, if both tests were used in a group of 1000 women with abnormal menstrual bleeding, 300 with fibroids or polyps, 27 of the 300 women with polyps/fibroids will be missed by 2D SIS, and 9 of 300 will be missed by 3D SIS.
3D SIS is an alternative to 2D SIS for which the technology and appropriate expertise are available. Both 2D SIS and 3D SIS should be considered alternatives to diagnostic hysteroscopy when intracavitary pathology is suspected in subfertile women and in those with abnormal uterine bleeding.
Low-quality evidence suggests that 3D SIS may be very accurate in detecting intracavitary abnormalities. Meta-analysis revealed no statistically significant differences between 2D SIS and 3D SIS. Summary sensitivity and summary specificity are higher for 3D SIS, but margins of improvement are limited because 2D SIS is already very accurate. When the technology and appropriate expertise are available, 3D SIS offers an alternative to 2D SIS. Both 2D SIS and 3D SIS should be considered alternatives to diagnostic hysteroscopy when intracavitary pathology is suspected in subfertile women and in those with abnormal uterine bleeding.
Focal abnormalities most commonly acquired within the uterine cavity include endometrial polyps (arising from the endometrium) and submucous fibroids (arising from the myometrium). These benign abnormalities can cause several problems, including abnormal uterine bleeding (AUB) and subfertility. Two-dimensional saline infusion sonography (2D SIS) is a minimally invasive test that can be used to diagnose these pathologies, but it is less accurate than hysteroscopy, which is a more invasive procedure by which an endoscope allows direct visualisation of the uterine cavity. Three-dimensional (3D) SIS appears to enhance sonographic visualisation within the uterine cavity, thereby offering a potentially more accurate minimally invasive diagnostic test.
Primary objectives
• To evaluate the diagnostic accuracy of 3D SIS (index test 1) compared with 2D SIS for the diagnosis of focally growing lesions (presence or not) in women with AUB or subfertility, with hysteroscopy performed as the reference test.
• To evaluate the diagnostic accuracy of 2D+3D SIS (index test 2) compared with 2D SIS for the diagnosis of focally growing lesions (presence or not) in women with AUB or subfertility, with hysteroscopy performed as the reference test. In this case, any abnormality on either modality was regarded as a positive result (‘OR’ approach).
Secondary objectives
• To evaluate the diagnostic accuracy of 3D SIS (index test 1) compared with 2D SIS according to type of abnormality and discrimination between uterine polyps and submucous fibroids in women with AUB or subfertility, with hysteroscopy and histology used as the reference.
• To evaluate the diagnostic accuracy of 2D+3D SIS (index test 2) compared with 2D SIS according to type of abnormality and discrimination between uterine polyps and submucous fibroids in women with AUB or subfertility, with hysteroscopy and histology used as the reference.
We searched the following databases: Cochrane Central Register of Studies Online (CENTRAL CRSO), MEDLINE, Embase, PubMed, Cochrane Gynaecology and Fertility Group (CGF) Specialised Register and CGFG Diagnostic Test Accuracy (DTA) Specialised Register, clinicaltrials.gov and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). Screening reference lists of appropriate studies was also performed. We screened for eligibility all studies identified from inception until March 2016. We performed searches with no date or language restrictions.
The population of interest consisted of premenopausal women with AUB or subfertility and postmenopausal women with AUB. Diagnostic test accuracy studies, randomised controlled trials (RCTs) and prospective cohort studies were eligible for inclusion if they evaluated the accuracy of both 2D SIS and 3D SIS for the diagnosis of acquired intracavitary abnormalities with hysteroscopy used as the reference standard. In light of the lack of data for 3D SIS, we also included studies that evaluated the accuracy of 3D SIS alone.
Two review authors read all potentially eligible references after performing a first screening by title and abstract (LLN and FJRH). They independently extracted data to construct 2×2 tables from eligible studies and assessed studies for methodological quality using the QUADAS-2 tool (revised tool for quality assessment of diagnostic accuracy studies). To describe and visually present results, we produced in RevMan forest plots showing pairs of sensitivity and specificity together with 95% confidence intervals from each study, as well as raw receiver operating characteristic (ROC) plots. We displayed paired analyses in an ROC plot by linking sensitivity-specificity pairs from each study by using a dashed line. To compare 3D SIS versus 2D SIS, we restricted analyses to studies that provided 2×2 tables for both tests and used the bivariate meta-analysis of sensitivity and specificity.
Thirteen studies (1053 women) reported the accuracy of 3D SIS for focal uterine abnormalities; 11 of these (846 women) were suitable for meta-analysis, and eight reported accuracy according to the type of focal abnormality. The design of the included studies seems applicable. The main problem involving the quality of included studies is insufficient reporting of study methods, resulting in unclear risk of bias for several of the quality domains assessed. Therefore, we considered the overall quality of the evidence as low. The summary estimate (11 studies reporting absence or presence of abnormality at 3D SIS) for sensitivity was 94.5% (95% confidence interval (CI) 90.6% to 96.9%) and for specificity 99.4% (95% CI 96.2% to 99.9%). Meta-analysis of the eight studies (N = 716) directly comparing 2D SIS versus 3D SIS showed summary sensitivity of 96.9% (95% CI 91.9% to 98.8%) and summary specificity of 99.5% (95% CI 96.1% to 100%) for 3D SIS. For 2D SIS, summary sensitivity was 90.9% (95% CI 81.2% to 95.8%) and summary specificity was 96.3% (95% CI 86.1% to 99.1%). The difference in accuracy between 2D SIS and 3D SIS was non-significant (P values of 0.07 for sensitivity and 0.10 for specificity).