Diagnostic Biochemistry and Clinical Medicine: Facts and Fallacies

In this paper we have attempted to define the relationships between clinical medicine and diagnostic or, as it is more frequently termed, clinical biochemistry. We have indicated first, the role that general biochemistry has played in elucidating mechanisms of disease and in providing the clinician with procedures that aid him in the diagnosis of disease and in the care of the patient. We have illustrated this role by reviewing very briefly some of the recent contributions such as the expanded diagnostic use of serum enzymes; the correlation of subcellular structure in human tissues with function at enzymatic levels; the investigation of enzyme variants; the metabolism of epinephrine and norepinephrine in pheochromocytoma; the metabolism of tryptophan in malignant carcinoid; and enzyme defects in hereditary disease. We noted the reservations with which the clinician frequently views the specific results that he obtains from the diagnostic biochemistry laboratory and have attempted to analyze the bases for these reservations. In this connection we considered the phenomenon of interlaboratory variability, the nature of the random and the constant errors that may exist within a laboratory, and the measures that the clinical biochemist may take to counteract these errors. We have tried to indicate the steps the clinician may take in a fuller and more knowledgeable utilization of the data from the diagnostic biochemistry laboratory. These involve a recognition of the efforts and advances that are being made in increasing precision and accuracy within the laboratory and the role that the clinician himself can play in contributing to this precision and accuracy. The phenomenon of intraindividual and interindividual variability of biochemical parameters, and the significance of this phenomenon in diagnosis, are also worthy of the clinicians attention. Finally, the clinician should abjure the concept that a seeming discrepancy between his formulation and laboratory results usually means a laboratory error. Thoughtful review, in cooperation with the biochemist, of such discrepancies are of value both for clinical medicine and clinical biochemistry.