The inter-observer reproducibility of Shafer's sign

Area of Science:

• Ophthalmology
• Retinal Surgery
• Diagnostic Accuracy

Background:

• Shafer's sign, characterized by pigment cells in the anterior vitreous, is a known indicator of retinal breaks.
• Assessing the reproducibility of Shafer's sign among different ophthalmic professionals is crucial for clinical practice.

Purpose of the Study:

• To evaluate the inter-observer reliability of Shafer's sign detection across varying levels of ophthalmic staff.
• To determine the diagnostic accuracy of Shafer's sign compared to confirmed retinal breaks.

Main Methods:

• A cohort of 47 patients were examined for Shafer's sign by a consultant vitreo-retinal surgeon, a senior house officer (SHO), and an optician.
• Cohen's kappa statistic was used to quantify agreement between examiners and between sign assessment and the presence of retinal tears.
• Sensitivity and specificity were calculated for consultant assessment against fundoscopy findings.

Main Results:

• Moderate agreement (kappa = 0.55) was observed between consultant and SHO assessments of Shafer's sign.
• Fair agreement (kappa = 0.28) was found between consultant and optician assessments.
• Consultant assessment demonstrated high diagnostic accuracy (sensitivity 93.8%, specificity 93.5%) with good agreement (kappa = 0.86) with the presence of retinal breaks.

Conclusions:

• The reliability of Shafer's sign assessment is influenced by the examiner's training and experience.
• While consultants show high accuracy, caution is advised regarding over-reliance on Shafer's sign, especially by less experienced staff.