Outcomes of Coccidioides Seropositive Solid Organ Transplant Recipients After Self-discontinuation of Antifungal Prophylaxis: The EIA-IgM-only Conundrum.

BACKGROUND

Solid organ transplant recipients are at risk of severe coccidioidomycosis and are given prophylaxis to mitigate the risk. Patients with seropositive testing typically receive lifelong prophylaxis; currently, this prophylaxis strategy includes patients who are positive only for IgM by enzyme immunoassay (EIA-IgM-only), although this result may be falsely positive.

METHODS

We conducted a retrospective study at a large-volume transplant center in an endemic coccidioidomycosis region to compare outcomes of non-lung transplant recipients who were seropositive for Coccidioides but discontinued prophylaxis (case patients) to outcomes of patients who continued prophylaxis (controls).

RESULTS

No case or control patients developed active coccidioidomycosis during the follow-up period. Before transplant, 62 of 77 case patients (80.5%) had a single positive serologic test, of whom 27 of 62 were EIA-IgM-only positive (43.5%). In contrast, 57 of 77 controls (74.0%) had a single seropositive result (16/57 [28.1%] were EIA-IgM-only). The single EIA-IgM-only result was classified as falsely positive by infectious disease consultants in 20 of 43 patients (46.5%) compared with all other Coccidioides serologic results (13/111 [11.7%], P  < 0.001). Lifetime antifungal prophylaxis was felt to be unnecessary for 28 of 43 patients (65.1%) who were EIA-IgM-only versus 31 of 111 patients (27.9%) with other serologic results ( P  < 0.001).

CONCLUSIONS

For patients repeatedly positive for EIA-IgM-only and no evidence of seroconversion, compatible clinical illness, or radiographic findings, discontinuing antifungal prophylaxis may be reasonable after the first posttransplant year.