Another candidate for the "top 10".

Although I do not disagree with any of the instruments chosen by Roy Midyett in his excellent article, "Ten instruments that changed the lab," [MLO, May 2005, p. 30], I suggest that there is at least one instrument that he overlooked that, in my opinion, deserves to be on the list, or at least an honorable mention (i.e., the Abbott TDx analyzer).

At the outset, permit me to state that I do not now nor have I ever had any financial relationship of any kind with Abbott Laboratories. My inclusion of the Abbott TDx on the list of the 10 instruments that most changed the lab is based solely on its significant contributions to the fields of therapeutic drug monitoring (TDM) and pharmacokinetics. In my view, the TDx revolutionized the quantitative measurement of a wide variety of clinically important drugs (e.g., digoxin) that prior to its introduction were, at worst, either not available at all or, at best, available only using cumbersome, time-consuming wet chemistry or recording spectrophotometric methods (e.g., salicylates). These methods provided relatively poor turnaround time of test results compared to the fully automated, analytically sensitive and specific TDx drug methods.

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Moreover, prior to the advent of the TDx, the science of clinical pharmacokinetics was in the Dark Ages compared to the renaissance that followed the introduction of the TDx instrument with its rapid and accurate methods for quantifying drug levels in peak and trough patients' specimens. From the time of its introduction into most clinical laboratories in the United States (circa 1980s) to the present, countless patients have benefited from the ability to more accurately monitor their therapeutic drug concentrations and avoid both under- and overdosing events.

Many of the readers of MLO of my generation remember fondly the acquisition of the TDx analyzer, with its distinctive "breadbox" shape. In addition, the novel principle [i.e., fluorescence polarization immunoassay (FPIA) (1)] on which TDx drug assays are based has been used to expand the menu of clinically useful tests to new drugs (e.g., cyclosporine A) and beyond [e.g., nondrug tests, such as the surfactant:albumin (S/A) ratio]. Clearly, the TDx has "earned" an important place in the history of laboratory instrumentation and medicine.

Reference

1. Jolly ME, Troupe SD, Wang CH, et al. Fluorescence polarization immunoassay. I. Monitoring aminoglycoside antibiotics in serum and plasma. Clin Chem. 1981;27:1190-1197.

--Frank H. Wians, Jr., PhD, MT (ASCP), DABCC, FACB

Professor of Pathology

Director, Clinical Chemistry

Associate Director,

Division of Clinical Pathology

Editor-in-Chief, LABMEDICINE

Department of Pathology

UT Southwestern Medical Center

Dallas, TX

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