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INTRODUCTION

No textbook in laboratory medicine would be complete without a description of methods used in the clinical laboratory. The methods described in this chapter are predominantly the common ones found in clinical laboratories. Each method description provides an overview of the basic concept of the assay, minimizing the details, while including clinically important information and a comment on the expense of the test and the complexity of the assay in the laboratory.

Some methods describe specific assays used almost exclusively in the clinical laboratory. For example, the PT and PTT are tests used for clinical assessment, with the goal to identify factor deficiencies in the coagulation cascade. Other methods are standard techniques used inside and outside the clinical laboratory. As an example, flow cytometry is a standard technique used in a variety of settings, and in this chapter it is shown how it is used in clinical laboratory testing.

Some tests are performed outside the laboratory in the vicinity of the patient. These tests are called “point-of-care tests,” commonly abbreviated as POCT. This section contains illustrations for point-of-care testing for glucose and for point-of-care testing for a variety of compounds that can be detected by immunological methods (immunoassays).

There is rapid growth of testing in the clinical laboratory for genetic alterations. These laboratory studies are often highly complex and very expensive, and it is difficult for most clinical laboratories to perform them for these reasons. In addition, the clinical impact of many genetic alterations remains unknown. Therefore, it is not uncommon for a genetic test, especially an assay involving gene sequencing, to produce results that have no known clinical significance. Selected genetic methods for detection of mutations and for gene sequencing are illustrated in this chapter.

The expense assessment attached to each assay described in this chapter is an approximation, listed as low, moderate, or high. It should be understood that the charge for the test set by the institution operating the laboratory is usually proportional to the expense of the reagents, supplies, and labor required to perform the test. On occasion, however, there is a great disparity between the actual expense to perform the test and the amount charged by the institution for the assay. With this in mind, the expense estimation provided for each method in this chapter is more closely related to the actual cost of reagents, supplies, and labor in the laboratory, with the understanding that the amount charged for the test should be in the same range of low, moderate, or high—but it is not always the case.

Each method also has a descriptor to reflect whether it is manual, semiautomated, or highly automated. A comment has been added if microscopy is involved, as this makes any technique highly manual. It should be noted that for some methods, there is an option for manual performance or for using some level of automation. ...

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