LABORATORY TESTS

 Common laboratory studies are usually simple measurements to determine how much or how many analytes, (a

substance dissolved in a solution, also called a solute) are present in a specimen. Laboratory tests are ordered

by practitioners to:

•  Detect and quantify the risk of future disease
•  Establish and exclude diagnoses
•  Assess the severity of the disease process and determine the prognosis
•  Guide the selection of interventions
•  Monitor the progress of the disorder
•  Monitor the effectiveness of the treatment

 The clinical value of a test is related to (Fischbach, 2000):

1.  Specificity—the ability of a test to correctly identify those individuals who do not have the disease
2.  Sensitivity—the ability of a test to correctly identify those individuals who have the disease
3.  Incidence—the prevalence of a disease in a population or community. the predictive value of the same test can be different when applied to people of differing ages, genders, and geographic locations.
4. 4. Predictive value—the ability of screening test results to correctly identify the disease state—a true-positivecorrectly identifies persons who actually have the disease, whereas a true-negative correctly identifies persons who do not actually have the disease.

 Laboratory test results are based on normal range values. Le Système International d’Unités (SI), the International System of Units, is an international normal range reference established for reporting laboratory results (Pagana & Pagana, 1999). For example, the SI reference range for reporting red blood cell count for a woman is 4.0 to 5.2 × 1012/L, the conventional range would appear as 4,000,000 to 5,200,000/mm3 of blood.