Lack of Association Between Histoplasma Urine Antigen Values and Clinical Response in Persons Without HIV
Marisa H Miceli1, Liam M Dalton1, Alessandro C Pasqualotto2,3
1Division of Infectious Diseases, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA.
Background:
Histoplasma urine antigen detection, a valuable diagnostic tool, is often used to monitor response to antifungal therapy, but persistently positive antigen values, even when the infection has resolved, often present a clinical conundrum for clinicians. We sought to better define the course of urine antigen values in patients who do not have HIV and to evaluate whether changes correlate with resolution of infection.
Methods:
Retrospective review of urine antigen tests and time to resolution of histoplasmosis for patients without HIV who were hospitalized between 1 January 2015 and 1 February 2024, and who had >2 sequential urine antigen tests performed.
Results:
Twenty-seven patients were included: 24 (89%) had disseminated infection and 23 (85%) were immunocompromised. Antigen values were followed for as long as 39 to 58 months in some patients. Changes in antigen values over time roughly fell into 3 groups. For 7 patients, the decrease in antigen corresponded with clinical response. Five patients, whose initial antigen levels were above the assay's level of quantification, had persistence at this high level for up to 15 months after clinical response. For the remaining 15 patients, antigen slowly decreased, sometimes transiently increased, not mirroring the clinical response; 4 patients had persistent antigenuria for as long as 22 to 48 months after all symptoms, signs, and laboratory abnormalities had resolved.
Conclusions:
These results support the concept that persistently positive Histoplasma urine antigen values, even very high levels, need not be the rationale for continued treatment in patients who have clinically responded and have completed recommended therapy.
