Methodological quality of the review: High confidence

Author: Virgili G, Menchini F, Dimastrogiovanni A.F, Rapizzi E, Menchini U, Bandello F, Chiodini RG.

Region: Details not provided

Sector: Optical coherence tomography, diabetic retinopathy complications.

Sub-sector: Steroscopic fundus photography and biomicroscopy, clinically significant macular oedema, Diabetic retinopathy diagnosis.

Equity focus: None specified

Review type: Effectiveness review

Quantitative synthesis method: Narrative analysis

Qualitative synthesis methods: Not applicable

Background

Optical coherence tomography (OCT) has gained increasing popularity as an objective tool to measure retinal thickness and other aspects associated with macular oedema. An advantage of using OCT is its quantitative assessment, rather than the qualitative evaluation performed with photography or biomicroscopy. In fact, less than optimal diagnostic performances can be expected in a clinical practice when such qualitative methods are used by untrained physicians.

It is worth summarizing the large amount of literature published on this topic in a systematic review to investigate whether OCT may perform as well as fundus photography or its surrogates to diagnose clinically significant macular oedema (CSME), allowing it to become an objective and quantitative alternative to this gold standard.

Research objectives

‘To review systematically the sensitivity and specificity of optical coherence tomography (OCT) for diagnosing macular oedema attributable to diabetic retinopathy compared with well-established gold standard tests such as stereoscopic fundus photography or contact and noncontact fundus biomicroscopy’.

‘The secondary purpose of this review was to investigate potential sources of heterogeneity of the estimates of sensitivity and specificity among diagnostic studies.’

Main findings

The authors included 15 studies in the review, which addressed CSME. The included studies were of good quality for most items of the QUADAS checklist, but most studies did not report masking of examiners and did not describe how withdrawals and undetermined results were treated. The expected operating point on the summary receiver operator characteristic, a pooled estimate of all studies, corresponded to a sensitivity of 0.79 (95% CI: 0.71– 0.86), a specificity of 0.88 (95% CI: 0.80–0.93), a positive likelihood ratio of 6.5 (95% CI: 4.0 –10.7), and a negative likelihood ratio of 0.24 (95% CI: 0.17– 0.32). These values suggest a good overall performance of OCT for diagnosing CSME.

OCT performed well compared with stereoscopic fundus photography or biomicroscopy to diagnose clinically significant diabetic macular oedema, particularly its central type. It was useful to decide on lase photocoagulation in patients with intermediate suspicion of disease.

The strength of this conclusion was limited by the reporting of the included studies, and authors should have presented cross tabulations of index and reference test results. Data adjusted for within-subject correlation should also have been provided, although this issue represented a challenge for systematic reviewers.

Several suggestions for further research were reported by the authors. Most of them referred to the quality of reporting and highlight the need to disseminate the Standards for Reporting of Diagnostic Accuracy initiative among authors of diagnostic studies in ophthalmology.

Methodology

The reference tests considered as a valid gold-standard for this review were stereoscopic fundus photography and contact lens or noncontact lens biomicroscopy of the fundus. Studies were included if definitions of the target disease set by the authors were met, reference test as mentioned above and index test (OCT low- or high-resolution) were met.

The authors searched MEDLINE (PUBMED 1966 – September 2006) and EMBASE (2002 – October 2006). They also manually searched the index of the following journals from 1998 to 2006: Ophthalmology, Archives of Ophthalmology, American Journal of Ophthalmology, Investigative Ophthalmology and Visual Science, British Journal of Ophthalmology, and Retina. The authors also manually searched the references of the articles obtained in full.

The assessment of the titles and abstracts for eligibility and the methodological assessment of the included studies based on QUADAS checklist were conducted by two independent reviewers.

Applicability/external validity

The authors did not discuss the applicability/external validity of findings.

Geographic focus

The geographical location of the studies was not addressed by the authors.

Quality assessment

The authors searched two main databases, hand searched the index of relevant journals and references of the articles obtained in full. Study selection, data extraction and appraisal of included studies were appropriately conducted minimising risk of bias. Although the methodological quality of the eligible studies was good, authors reported a few issues regarding the quality of the same as a concern. Therefore, overall, there was high confidence in the conclusions about the effects of this study.