Accuracy of diagnosing early ocular surface squamous neoplasia using methylene blue in Zambia

Abstract

Background: Ocular surface squamous neoplasia (OSSN) includes pre-invasive and invasive squamous lesions of the ocular surface. Current diagnosis relies on surgical excision and histology, with potential complications. This study assessed the reliability of methylene blue staining as a non-invasive diagnostic tool for OSSN at the University Teaching Hospitals – Eye Hospital in Lusaka, Zambia.

Aim: This study aimed to evaluate the accuracy of methylene blue staining in diagnosing OSSN.

Setting: The study took place at the University Teaching Hospitals-Eye Hospital, Lusaka, Zambia, between February 2022 and February 2023.

Methods: A cross-sectional study design compared methylene blue staining to histology in diagnosing OSSN. Participants underwent staining before excision biopsy on the same day. Data were analysed using SPSS and SAS OnDemand, employing Chi-square and McNemar’s tests for paired diagnostic test comparison.

Results: The study involved 79 participants, with a high OSSN prevalence (62%), primarily among females (62%), with an average age of 40. Ocular surface squamous neoplasia correlated significantly with employment (P = 0.02) and HIV infection (P = 0.03). The most common symptom was nasal conjunctival growth. Duration of symptoms did not consistently indicate disease severity. Methylene blue staining showed 87.8% sensitivity, 83.33% specificity, a positive predictive value of 89.6%, and a negative predictive value of 80.7%.

Conclusion: Methylene blue staining is an effective alternative diagnostic method for OSSN, offering high accuracy. However, it cannot replace histology.

Contribution: This study contributes valued insights into the reliability of methylene blue staining for diagnosing OSSN and delineation of surgical margins during excision biopsy.