Ocular Microbiology and Immunology Group
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POSTER PRESENTATION

False Positive Acanthamoeba keratitis from Multiplex PCR Diagnostics: A Case Series

Ashlin Joye^1,2, Alejandro Arboleda^1,3, Thuy Doan¹, Gerami Seitzman<sup>1

1</sup>UCSF Proctor Foundation, San Francisco, California; ²Devers Eye Institute, Portland, Oregon; ³Baylor University, Houston, Texas

Purpose: To demonstrate a series of four cases where multiplex PCR resulted in false positive diagnoses of Acanthamoeba keratitis.

Methods: This case series describes the clinical course of four patients initially misdiagnosed with Acanthamoeba keratitis in the setting of a positive Acanthamoeba result on multiplex PCR (HealthTrackRx, Denton, TX). After referral to our tertiary care center, additional diagnostic tools including history taking, slit lamp examination, in vivo confocal microscopy, and corneal scraping diagnostics including metagenomic deep sequencing, were performed to aid in diagnosis and management of the patients.

Results: All patients presented to the clinic on topical antiparasitics (chlorhexidine) after receiving a diagnosis of Acanthamoeba keratitis at an outside clinic. After referral, each patient was evaluated - patients 1 and 2 received an infectious keratitis workup and patient 3 an anterior scleritis workup. Patients 1 and 2 were switched to polyhexamethylene biguanide (PHMB) after initial evaluation at our clinic, and patients 3 and 4 were discontinued off chlorhexidine after initial examination. Utilizing all evaluation metrics noted above, the final diagnoses for the patients were Staphylococcus marginal keratitis for patient 1, recurrence of HSV keratitis for patient 2, anterior scleritis for patient 3, and neurotrophic ulcer for patient 4. All four patients recovered within weeks following correct identification of the disease entity.

Conclusions: Multiplex PCR from an ocular surface swab is an imperfect diagnostic tool and may pose unique challenges for eye care providers due to false positive results. Each case highlights the importance of integrating patient history, clinical examination, and appropriate diagnostic tools when managing patients with complex disease. Further investigation is needed to evaluate the potential benefits and downsides of utilizing multiplex PCR arrays for the diagnosis of ocular infections.