To the Editor—We thank Hamilton [1] for asking how a global immunity test provides added benefit over stratifying the risk of infection based on the prednisone dosage after transplantation. In organ transplant recipients, the risk of opportunistic infection is determined in large part by the “net state of immunosuppression”[2]. Many factors contribute to this net state, including a variety of immunosuppression drugs, such as antilymphocyte globulin, calcineurin inhibitors, antiproliferatives, and others. In addition, factors such as renal failure, concomitant viral infection, and drug-induced leukopenia also contribute. The test used in the study by Mian et al [3] reflects interferon γ production from both adaptive and innate immune arms and thereby is one attempt to measure the net state of immunosuppression. Therefore, although higher dosages of prednisone do likely result in an increased risk of infection, this is only one of many contributing factors and is therefore likely to be only a crude predictor. In fact, after 3 months, many patients are on a regimen of≤ 10 mg prednisone daily and continue to acquire opportunistic infections despite the relatively low prednisone dosage.

As requested, we have analyzed opportunistic infection rates in patients receiving high-versus low-dose prednisone (> 20 vs≤ 20 mg per day). There was no significant difference in the rate of opportunistic infections 1–3 months after transplantation in patients receiving high-versus low-dose prednisone (11.1% vs 13.4%; P=. 99). The overall infection rates were also similar in these 2 groups (38.9% vs 25.2%, respectively; P=. 22). After 3 months, only 2 patients were receiving prednisone at a dosage of> 20 mg, so a similar analysis was not possible for subsequent time points. In summary, given that multiple factors contribute to immunosuppression, a test for global immunity is more likely to personalize how we risk-stratify patients for