Combination of Simple Diagnostic Tests to Detect Primary Angle Closure Disease in a Resource-constrained Region

ABSTRACT

Purpose: To report on diagnostic accuracy of van Herick (vH) technique performed by a vision technician (VT) as well as on efficacy of a combination of vH technique and central anterior chamber depth (ACD) in detection of primary angle closure disease.

Methods: Data was obtained from two cohorts; rural clinic setting (n = 111), and rural population-based research setting (n = 888). Van Herick grading was performed by a VT in first cohort and a glaucoma specialist in second cohort. A reference standard four-mirror gonioscopy was performed by a glaucoma specialist in both cohorts. We did preferential sampling. Cut-off levels for vH technique and central ACD were grade 2 and 25^th percentile value, respectively. Data from one eye per participant was analyzed.

Results: Three hundred and forty (34%) eyes were gonioscopically occludable. Area under receiver operating characteristic curve (95% confidence interval) for vH test was 0.83 (0.76, 0.9) and 0.81 (0.78, 0.84) in first and second cohorts, respectively. Simultaneous testing achieved sensitivity of 87.8% while sequential testing achieved specificity of 99.3%. Negative predictive value* of simultaneous testing was 98.3% compared to 96.6% of vH technique while positive predictive value* of sequential testing was 86% compared to 49.3% of vH technique. (*at 10% prevalence of gonioscopically occludable angle)

Conclusions: Diagnostic accuracy of vH grading was similar when performed by a VT and a glaucoma specialist. While test combination was effective to rule in, vH technique may suffice to rule out the disease. Implications of these findings for resource-constrained regions are discussed.

KEYWORDS:

• Van Herick technique
• Limbal anterior chamber depth
• primary angle closure Glaucoma
• Glaucoma screening
• test combination