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| TEXT BOOK of MEDICINE |
| APPENDIX: REFERENCE INTERVALS AND LABORATORY VALUES* Ronald J. Elin |
Reference intervals are valuable guidelines for the clinician to assess health and disease, but they should not be used as absolute indicators of health and disease. For essentially every test, significant overlap exists between healthy and diseased populations. Many factors may influence the determination of the reference interval. The method and mode of standardization are variables for the reference interval, particularly for immunologic and enzymatic tests. The selection of the “normal” population is also important because factors such as age, gender, race, diet, personal habits (e.g., alcohol consumption, smoking), and exercise may influence the reference interval for a given analyte. Finally, the statistics chosen to define the reference interval are also a factor. These multiple variables for determining the reference interval indicate why differences exist among institutions for the same analyte.
The values in this chapter are primarily for adults in the fasting state. Values for other groups, when included, are clearly identified. Prefixes and abbreviations are listed in Table Appendix-1. For convenience, this chapter is divided into the following three sections: clinical chemistry, toxicology, and serology (Table Appendix-2); hematology and coagulation (Table Appendix-3); and drugs, therapeutic and toxic (Table Appendix-4). The list includes reference intervals for the most common tests used in the practice of internal medicine.
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All laboratory values are given in conventional and international units. If the value and units for a reference interval are the same for conventional and international units, the interval is listed only in the column for international units. The temperature for all enzyme assays listed in the chapter is 37° C. The pertinent prefixes denoting the decimal factors and abbreviations are listed in Table Appendix-1.
SUGGESTED READINGS
Burtis CA, Ashwood ER, Bruns DE (eds): Tietz Textbook of Clinical Chemistry and Molecular Diagnosis, 4th ed. St. Louis, Elsevier Saunders, 2006. A comprehensive text.
Wu AHB (ed): Tietz Clinical Guide to Laboratory Tests, 4th ed. St. Louis, Elsevier Saunders, 2006. A comprehensive text of reference intervals.
*The material in this chapter was partially extracted from Tietz NW (ed): Clinical Guide to Laboratory Tests. Philadelphia, WB Saunders, 1995. The material for the section on therapeutic drug concentrations was partially extracted from Burtis CA, Ashwood ER (eds): Tietz Textbook of Clinical Chemistry, Philadelphia, WB Saunders, 1994. The main contributors to this section of the book are P. C. Painter, J. Y. Cope, and J. L. Smith. Other sources are listed under the suggested readings for this chapter.