Abstract
<title>Abstract</title> <p> <bold>Background</bold> Patients after lung transplantation are at high risk for cytomegalovirus retinitis (CMVR) because of long-term immunosuppression. The (1,3)-β-D-glucan (G) test is widely used to screen for invasive fungal infection, but non-fungal factors such as vitreous hemorrhage may cause false-positive results. <bold>Case presentation</bold> We report a 55-year-old man who presented with sudden blurred vision in the right eye one year after lung transplantation for pneumoconiosis. CMVR was confirmed in both eyes, and the right eye was complicated by vitreous hemorrhage and rhegmatogenous retinal detachment. Intraocular fluid testing showed strongly positive CMV-DNA and a positive (1,3)-β-D-glucan (G) test (293.43 pg/mL) in the right eye, while fungal culture and the galactomannan (GM) test were negative. The left eye was positive for CMV-DNA but negative for the G test. After intravitreal ganciclovir injections and pars plana vitrectomy in the right eye, the G test became negative. Later, when the left eye developed a sudden drop in vision and vitreous hemorrhage, the G test became transiently positive again and turned negative after clearance of the hemorrhage. <bold>Conclusions</bold> Vitreous hemorrhage can cause false-positive G test results through mechanisms including nonspecific activation by blood components, alterations in the intraocular microenvironment, and physicochemical interference from the specimen; false-positive results are more common when G test values are <1000 pg/mL. Positive intraocular G test results in lung transplant recipients with CMVR and vitreous hemorrhage should therefore be interpreted with caution, and a comprehensive assessment combining fungal culture, the GM test, and dynamic monitoring is necessary to avoid unnecessary antifungal therapy. Early intraocular fluid CMV-DNA testing for definitive diagnosis, combined with local antiviral therapy and surgery, is key to improving the prognosis. </p>