Beta-D-Glucan testing may help diagnose some Fungal Endophthalmitis cases outside screening paradigm

Fungemia is more commonly observed in patients who are on chronic total parenteral nutrition or those who are immunocompromised, such as those with diabetes mellitus, malignancy, chronic steroid use, or those with human immunodeficiency virus (HIV). As the prevalence of patients with health conditions that put them at risk for fungal infections increases, it becomes increasingly important for rapid identification and treatment of systemic fungal infections and evaluation of possible ocular involvement. Since patients with fungemia may develop asymptomatic ocular involvement, the current recommendation from the Infectious Disease Society of America is for patients who have positive fungal blood cultures to undergo ophthalmic examination to evaluate for intraocular fungal infection.

Recently, the beta-D-glucan (BG) assay has been used as a screening device for systemic fungal infections. The BG test is a quantitative assay approved by the Food and Drug Administration in 2004, and its goal is to provide early detection of invasive fungal infections. As fungal species divide, the fungal cell wall is continuously remodeled and some BG is released into the bloodstream and can aid in the detection of systemic fungal infections.

In comparison, fungal cultures rely on growth of an entire organism rather than identification of molecular marker. Depending on the media used, the time to detection of fungal species in blood cultures can vary greatly, from within 24 hours to over 100 hours, with varying sensitivity. Conversely, the BG test can be completed as quickly as 1 hour. However, the literature regarding the necessity for inpatient ophthalmology consultation to rule out fungal endophthalmitis in cases of elevated BG levels without fungal blood culture data at the time of consultation is limited.

This paper by Govindaraju et al reports the incidence of fungal endophthalmitis in patients who have elevated BG levels without fungal blood culture data at the time of consultation and in patients who have positive fungal blood cultures and the utility of ophthalmology consultation in patients with elevated BG levels.

Single center retrospective consecutive cohort study was conducted on patients at Beaumont Health from 2016–2021 who either had positive fungal blood cultures or an elevated BG level. A total of 147 patients were examined by the ophthalmology department where 30 patients had an elevated BG level and 100 patients had a positive fungal blood culture. Incidence of fungal endophthalmitis was 0% in the elevated BG group and 1.5% in the positive fungal culture group, corresponding to a relative risk ratio of 0.0 (p = 0.31).

As the life expectancy of the average adult continues to increase, so does the chance for developing health conditions that put them at risk for developing an invasive fungal infection. Proper care for these patients requires a multidisciplinary approach including internal medicine, ophthalmology, infectious disease, and potential other subspecialties depending on the underlying medical condition. Fungal infections, whether intraocular or extraocular, carry a high morbidity and mortality rate and rapid detection and treatment of such infections becomes paramount.

Within this report, a diagnosis of presumed fungal endophthalmitis was made at incidence of 0% in the elevated BG group and 1.5% in the positive fungal blood culture group, corresponding to a relative risk ratio of 0.0 (p = 0.31).

Out of the 3 eyes that had presumed fungal endophthalmitis, 1 patient had a history of cancer undergoing active chemotherapy and radiation while 2 patients had a history of diabetes and intravenous drug abuse. All three patients in the positive fungal culture group grew Candida albicans. None of the patients with presumed fungal endophthalmitis had an indwelling urinary catheter. There was one eye in the BG group where there was clinical suspicion of fungal endophthalmitis. However 4 days after the initial ophthalmic examination, fungal blood cultures did not grow any organisms but a blood culture did grow methicillin-resistant Staphylococcus aureus (MRSA). This patient was taken for vitrectomy due to worsening vision and aerobic, anaerobic, and fungal cultures were done on the vitreous sample which was negative for infectious etiology, however this was approximately 1 week after intravenous antibiotics and intravitreal administration of antibiotics and antifungals. Based on blood culture results, this may represent a case of bacterial endophthalmitis rather than fungal endophthalmitis.

The beta-D-glucan quantitative assay is a relatively new test that is gaining significant utility in critically ill patients. BG testing may be useful in diagnosing isolated cases outside the standard screening paradigm, however the data within this study support the conclusion that there is no compelling evidence at this time to add or use BG as a surrogate for endophthalmitis screening. Clinical correlation is crucial as there are multiple causes of a falsely elevated BG and these may lead to unnecessary examinations and overuse of invasive procedures which can be a significant cost to the patient. Continued study is needed to further elucidate the role of BG in guiding its use as ancillary testing and in ophthalmic screening exams for critically ill patients.

Source: Govindaraju et al; Clinical Ophthalmology 2022:16

https://doi.org/10.2147/OPTH.S362888