From The Earth Times:

The ability of blood tests to precisely measure very low doses of anti-rejection drugs in kidney transplant patients may make a significant difference in assuring long-term viability and survival, according to research presented today at the American Association for Clinical Chemistry (AACC) annual meeting.

The current thinking in transplant medicine favors reducing doses of tacrolimus and other immune-suppressive drugs as much as possible after kidney-transplant procedures. "Even though we are succeeding in preventing organ rejection, we haven't made much progress to improve long-term survival," said Sudarshan Hebbar, M.D., senior medical director, Abbott Diagnostics.  "Unfortunately, most kidney transplant patients will go back on dialysis in eight to ten years, in part because the anti-rejection drugs can be toxic to the kidneys."

Dr. Hebbar added that kidney-transplant patients have high incidence of heart attacks and other cardiovascular disorders from long-term effects of renal disease. Therefore, minimizing drug toxicity over time is considered one way to help improve long-term graft survival and preserve quality of life for transplant patients.

To minimize long-term toxicity of transplant medications, physicians frequently aim to taper down doses of immunosuppressive drugs to as low a level as possible without risking rejection. "Successful low-dose regimens of tacrolimus and other anti-rejection medications require highly precise, ultra-sensitive drug-monitoring assays," said Daniel Levine, Ph.D., director of the clinical laboratory, Iris and B. Gerald Cantor Clinical Research Laboratory at The Rogosin Institute in New York City.

Dr. Levine emphasized the importance of using an accurate and precise test to monitor patients on low-dose treatment regimens. "At low doses, even the slightest variation in blood-level readings could be devastating to transplant patients. The consequence for the laboratory is twofold: it must have accurate, precise testing for immunosuppressive drugs, and tacrolimus tests that are accurate to 4 ng/mL are no longer adequate," he explained.

Dr. Levine reported results of his studies evaluating the performance of the Abbott ARCHITECT assay for tacrolimus, the most widely used immunosuppressant drug. He said the usual dosing range for the medication is between 2 and 15 ng/mL, with lower doses preferred. "The challenge for the laboratory, therefore, is to assure with the utmost confidence to the physician that a tacrolimus blood level of 3 ng/mL is exactly right and not 5," Levine said.