Method for determining reference changes from patients' serial data: example of cardiac enzymes

• Published in: Clinical chemistry (Baltimore, Md.) Vol. 39; no. 11; pp. 2298 - 2304
• Main Authors: Kairisto, V, Virtanen, A, Uusipaikka, E, Voipio-Pulkki, LM, Nanto, V, Peltola, O, Irjala, K
• Format: Journal Article
• Language: English
• Published: Washington, DC Am Assoc Clin Chem 01.11.1993; American Association for Clinical Chemistry
• Subjects: Adolescent; Adult; Aged; Biological and medical sciences; Biomarkers; Computerized, statistical medical data processing and models in biomedicine; Creatine Kinase - blood; Female; Humans; Isoenzymes; L-Lactate Dehydrogenase - blood; Male; Medical sciences; Medical statistics; Middle Aged; Reference Values; Heart; Human; Statistical method; Reference system; Enzyme; Creatine kinase; Isozyme; Transferases; Variability; Calculation; Oxidoreductases; L-Lactate dehydrogenase
• ISSN: 0009-9147; 1530-8561
• DOI: 10.1093/clinchem/39.11.2298

Changes between serial laboratory test results can be significant, even if none of the individual results exceeds the reference interval. We developed a statistical method for the calculation of reference change limits from routine patients' data for situations in which the majority of the patients can be considered suitable reference subjects. The method was applied to cardiac enzyme data [creatine kinase (CK; EC 2.7.3.2), creatine kinase isoenzyme MB (CK-2), lactate dehydrogenase (LD; EC 1.1.1.28), and lactate dehydrogenase isoenzyme 1 (LD-1)] from 2029 consecutive patients. We used hospital discharge diagnoses to exclude patients with the diagnosis of myocardial infarction or myocarditis, but we also studied the characteristics of the method on unselected patients' data. The reference change limits derived from the diagnosis-selected patient group were as follows (U/L, activity measurements in serum at 37 degrees C according to Scandinavian recommendations): CK from -39 to 27, CK-2 from -8 to 7, LD from -86 to 85, and LD-1 from -19 to 15. Similar limits were obtained by conventional statistical methods from a group of 29 hospitalized patients with no myocardial symptoms. Our results suggest that it is possible to produce clinically applicable reference change limits from routine data.