Which laboratory finding would most directly indicate subtherapeutic immunosuppression?

• A. Immunosuppressant drug level below therapeutic range.
• B. WBC elevated.
• C. Potassium high.
• D. Hb low.

Answer: (A)

Maintaining immunosuppressant drug levels within a defined range is essential to provide enough suppression of the immune response to protect a transplanted organ while avoiding toxicity. The most direct indicator of subtherapeutic immunosuppression is the drug concentration in the blood falling below the therapeutic range, meaning there isn’t enough medication to adequately suppress the immune system. This is why the trough level of the immunosuppressant is monitored and adjusted to stay within the target window.

Elevated white blood cell count, high potassium, or low hemoglobin point to other issues—infection/inflammation, electrolyte imbalance, or anemia, respectively—not to whether the immunosuppressant level is adequate.