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Laboratory medicine will play a critical role in the workup of each of the above patients. The importance of the history and physical must not be understated, but the data often obtained from these activities are subjective or dependent on the patient and the stage of the condition. Furthermore, the signs and symptoms of many diseases are similar, so much so, that patients can be misdiagnosed or mismanaged without additional data. Consider, for example, the number of disorders that can cause the fatigue and weight loss reported by the patient in Case 7-1. Is the shortness of breath and chest pain reported in Case 7-2 due to a cardiac or respiratory problem?

CASE 7-1

GW is a 23-year-old woman who is seen by her family medicine physician following several months of increasing fatigue and generally not feeling well. She reports she has lost 16 lb over the past 6 months without dieting. She is applying to medical school and thinks this may be stress related.

CASE 7-2

RM is a 52-year-old man who presents to the emergency department with mild chest pain and shortness of breath. He reports that his symptoms began about 3 hours ago just before landing at the local airport after an 18-hour flight from Asia.

As will be seen, the tests ordered by their respective clinicians and the results reported by the clinical laboratory will make the diagnosis in one patient and will greatly influence additional decisions for the others. These are but two examples in which the judicious use of clinical laboratory testing proves to be one of the most effective and economical ways of acquiring objective data that can clarify many presentations. Today’s clinician has several thousand individual tests at his or her disposal.

The goal of this chapter is to introduce you to laboratory medicine and the clinical laboratory thus removing some of the mystery of what happens when you order a laboratory test or take a sample to the laboratory, and to help you understand how to better use and evaluate laboratory tests so that you will be more efficient and effective in ordering tests and interpreting results.


The use of this part of pathology, laboratory medicine (Figure 7-1), is so important to patient care that the clinical laboratories in the United States produce more than 7 billion test results each year that are used to derive a diagnosis, determine disease severity, assess risk factors, select and monitor interventions and treatments, formulate prognoses, and to evaluate or avoid potential adverse outcomes.


The role of laboratory medicine in patient care.


Laboratory medicine is the part of pathology typically associated with the provision of laboratory ...

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