Teaneck, New Jersey coronary care unit or a hospital wing with specialized cardiac care facilities. The standard diagnostic protocol for these patients included ...
Immunochemical LDX Assay for Myocardial Infarction MAJID ALI, M.D., EVALYNNE V. BRAUN, M.D., SALVATORE LARAIA, M.D., A. OLUSEGUN FAYEMI, M.D. DONALD J. NALEBUFF, M.D., AND PEGEEN H. PALLADINO, CLA(ASCP)
THE VALUE of the determination of lactic dehydrogenase (LD) isoenzymes in the diagnosis of myocardial infarction is well established. 61213 For this purpose, the electrophoretic technique is the most widely used method at present. The recently introduced immunochemical assay for LD, (heart-derived isoenzyme) appears to be a sensitive and specific method with additional advantages of procedural simplicity and statistics capability. 717 This study was undertaken to compare the diagnostic efficiency of the immunochemic and electrophoretic methods for determination of LD, in the diagnosis of acute myocardial infarction. Materials and Methods One-hundred consecutive patients hospitalized with a clinical suspicion of acute myocardial infarction were included in this study. Each patient was treated in the t '_h
Received December 9, 1^80: received revised manuscript and accepted for publication February 17, 1981. Address reprint reque|t?jto Dr. Ali: Department of Pathology, Holy Name Hospital, 718/Teaneck Road, Teaneck, New Jersey 07666. •?l"
Departments of Pathology, College of Physicians and Surgeons of Columbia University, Mount Sinai School of Medicine, New York City, and Holy Name Hospital, Teaneck, New Jersey and the Division of Medicine, Holy Name Hospital, Teaneck, New Jersey
coronary care unit or a hospital wing with specialized cardiac care facilities. The standard diagnostic protocol for these patients included serial electrocardiograms and serial determination of total CPK and LD activities and their isoenzymes at the time of admission and on two successive mornings. The cardiologist reading the electrocardiograms was unaware of the enzymatic studies until the full protocol was completed. Total CK and LD activities were determined with kinetic procedures using Beckman reagents and enzyme analyzer. Total LD activity was assayed using the lactate-to-pyruvate reaction; CK assays were performed by the method of Rosalki. 15 The electrophoretic fractionation of both LD and CK was performed with cellulose acetate electrophoresis* according to the manufacturer's directions. The electrophoresis strips were scanned with Helena Auto Scanner-Flur-VIS densitometer. The immunochemical LD, assays were performed using the Roche kit according to the manufacturer's directions. Briefly, in this procedure goat anti-LD 5 serum is incubated with the patient's serum for 5 min at ambient temperature to separate LD, from all LD isoenzymes containing the M subunit. In the second step, donkey anti-goat IgG conjugated to polyvinylidene fluoride floccules is added and incubated for 5 min at ambient temperature; the mixture is then centrifuged to remove LD isoenzymes containing the M subunit (LD 2 to LD 5 ). The analysis of the supernatant fluid for LD activity is, then, a measure of LD, in the test sample. To ascertain complete removal of all LD isoenzymes except LD, from the test sample by the primary and precipitating antibodies, LD electropherograms were prepared with sera from two patients with acute MI after incubation with the two antibodies. The CK electropherograms were examined under U.V. light and the results were recorded as CK-MB * Helena Laboratories, Inc., Beaumont, Texas.
0002-9173/81/0010/0426 $00.70 © American Society of Clinical Pathologists
426
Downloaded from http://ajcp.oxfordjournals.org/ by guest on November 1, 2016
AH, Majid, Braun, Evalynne V., Laraia, Salvatore, Fayemi, A. Olusegun, Nalebuff, Donald J., and Palladino, Pegeen H.: Immunochemical LD, assay for myocardial infarction. Am J Clin Pathol 76: 426-429, 1981. The diagnostic efficiency of an immunochemical assay for LD, (I-LD,) was compared with an electrophoretic procedure for this isoenzyme (E-LD,) in 100 consecutive patients hospitalized for a clinical suspicion of acute myocardial infarction (MI). All patients were investigated with a standard protocol including serial determinations of total creatine kinase (CK) and lactic dehydrogenase (LD) activities, CK and LD isoenzymes, and electrocardiograms. Thirty-two patients were diagnosed to have acute MI on the bases of positive CK-MB or EKG or both. The coefficients of variation for the intraassay and interassay precision of I-LD, assay ranged from 3.12% to 7.69%. Direct correlation between the I-LD, and E-LD, was very satisfactory (r = .961; P =
