1562. Impact of Skin Biopsy on Diagnosing Infections and Changing Treatment in Cancer Patients with New Skin Rash

Background Skin lesions in immunosuppressed cancer patients have a broad differential of infectious and non-infectious causes. Rash may be an early indication of serious systemic infections that are otherwise difficult to diagnose; hence, skin biopsy with culture and histopathology plays a vital role in establishing a diagnosis. Our study aims to determine the yield of skin biopsy in identifying infections and its impact on diagnosis and therapy. Methods We performed a retrospective review of all cancer patients admitted to University of Maryland from August 2010 to October 2017 who had a skin biopsy for new rash. We classified the skin lesion as infectious if the biopsy pathology or culture showed a pathogenic organism. Results Of 269 patients biopsied for new skin lesions, 43 (16%) were caused by infection and 226 (84%) were non-infectious. Among non-infectious causes, 63% were due to graft vs. host disease, 9% cancer, 9% drug reaction, 4% Sweet syndrome, and 29% were nondiagnostic. The median WBC count trended toward significantly lower in the infectious group (1,100/μL) vs. the non-infectious group (2,700/μL; P = 0.08). Of the 43 infectious lesions, 21 (49%) were fungal, 13 (30%) bacterial, seven (16%) viral and one (2%) mycobacterial. Sixty-seven percent patients had absolute neutrophil counts <1,000/μL, 40% were febrile, and 28% had had a stem cell transplant. The majority of infections (58%) were identified by skin biopsy alone. Change in diagnosis after biopsy was significantly more likely in patients with infectious cause of skin lesions than non-infectious (47% vs. 28%, respectively, P < 0.02). Patients with a biopsy-confirmed infectious cause were five times (95% CI 2.70–10.22) more likely to have a change in therapy post biopsy compared with patients with a non-infectious cause. The sensitivity and specificity of provider diagnosis prior to biopsy was 86 and 81%, respectively. The positive predictive value of pre-biopsy provider diagnosis was low at 46%. Conclusion Skin biopsy of new rash in immunocompromised cancer patients frequently reveals systemic infections (especially fungal) and often leads to a change in diagnosis and therapeutic management. Disclosures All authors: No reported disclosures.