Clinical Chemistry Laboratory Assays and their Role in Patient Diagnosis

Clinical Chemistry is one major section of the laboratory where substances in blood are tested and made use of as a tool in diagnosing diseases. Substance tested include various blood constituents, the most common of which are: glucose, creatinine, blood urea nitrogen, proteins, electrolytes, the cardiac panel test including Low Density Lipoprotein (LDL), High Density lipoprotein (HDL) triglyceride, cholesterol and others.

Enzymes are also tested to determine liver, cardiac and pancreatic functions. Some of these substances are: Lactate dehydrogenase (LDH), cholinesterase (CHS), alkaline phosphatase (ALP), gamma glutamyl transferase (GGT), 5’nucleotidase ( 5 NT) for liver function, creatine kinase (CK), aspirate amino transferase (AST) for cardiac function and amylase, lipase for pancreatic function.

These substances have normal levels/values in blood and any elevation or decrease in would usually indicate an existing pathologic condition. Values obtained from the laboratory tests are interpreted by the physician to diagnose diseases.

The Medical Technologist therefore, should be aware of the precautions involved for each substance in the performance of the assays. There are four phases involved in clinical chemistry which contribute to reliability of results. These are: Proper patient identification, correct sampling, accurate assaying, and correct reporting. For an assay to be considered reliable, it has to undergo these four processes. Hence, even the process of identification is very important for results to be considered accurate. The phlebotomist too has a vital role in ensuring that reliable results are obtained.

The role of clinical chemistry assays is therefore crucial to the correct diagnosis of a patient. If these assays are not performed, the doctor would not be able to rule out existing conditions.

One specific example is diabetes mellitus (DM). The possibility that DM could be diagnosed based on symptoms and other laboratory tests like urinalysis (in which glucose would be positive) is possible. But the doctor would never be certain of the exact concentration of glucose if it is not measured in the patient’s blood itself. The normal concentration of glucose is 60 110 mg/dL and any value that does not fall within this range is considered abnormal. This is also true for the other substances present in blood. If they don’t fall within the accepted reference ranges or normal values, then the patient is unhealthy.

All laboratory results from the other laboratory sections, the medical history of the patient and the physical symptoms should be considered; however, in arriving at the correct diagnosis of the patient’s condition. These laboratory assays – which are performed by the medical technologist in the clinical chemistry section-have a vital role in this complex process. The medical technologist should perform his responsibilities in congruence with other health allied workers to promote health and wellness in the society in which he exists in.