Diagnostic efficiency of four lactate dehydrogenase isoenzyme-1 ratios in serum after myocardial infarction

We compared the diagnostic efficacy of the ratios LD-1/LD-2, LD-1/LD-3, LD-1/LD-4, and LD-1/LD-5 in 69 documented cases of myocardial infarction. We used 149 patients with congestive heart failure and 67 patients with nonmyocardial infarct as controls. We used a computer program to produce receiver-operating characteristic curves, decision threshold plots, and likelihood ratios for these LD ratios at 6-h intervals up to 108 h after the onset of chest pain or hospital admission. All ratios in the myocardial infarction cases peaked around 36 h after the onset of chest pain, while those for the nonmyocardial and congestive cardiac failure cases did not change over the 108-h period. In all patients with infarctions, LD-1/LD-4 and LD-1/LD-5 increased by 1.7 times (when LD-1 was less than 40%) and 3.4 times (when LD-1 was greater than 40%), respectively, over control values. Optimum decision threshold values were obtained at 13-24 h (LD-1/LD-5), 31-36 h (LD-1/LD-4 and LD-1/LD-3), and 55-60 h (LD-1/LD-2) after onset of symptoms. The highest likelihood ratio was obtained with the LD-1/LD-4 ratio; therefore, we suggest that this is a better diagnostic test for myocardial infarction than LD-1/LD-2.     

Early diagnosis of acute myocardial infarction by rapid analysis of creatine kinase isoenzyme-3 (CK-MM) sub-types

We compared the clinical sensitivity, specificity, and diagnostic efficiency of measuring creatine kinase-3 (MM) isoenzyme sub-types (CK, EC 2.7.3.2) with the measurement of CK-2 (MB) isoenzymes for the diagnosis of acute myocardial infarction. Serial blood collections at 3-h intervals from 35 patients with acute myocardial infarction were examined. In attempts to reperfuse their coronary arteries, some of these patients were treated with pharmacological thrombolysis (streptokinase, tissue plasminogen activator), with or without coronary angioplasty. The infarction patients were divided into two groups: patients who were successfully treated with thrombolytic agents (i.e., they achieved coronary reperfusion), and patients who were treated unsuccessfully or who were not treated acutely. We also examined blood from 34 non-infarction patients. We measured CK-3 sub-types by both anion-exchange liquid chromatography and a modified high-voltage electrophoresis method, and CK-2 by immunoprecipitation. Our results show that during the first few critical 3 to 9 h after onset of chest pain, measurement of CK-3 sub-types has the highest diagnostic efficiency; in contrast, CK-2 has the highest efficiency during the 10- to 21-h time intervals. Thus early diagnosis of acute myocardial infarction can be based on rapid assays of CK-3 sub-types.     

Increased lactate dehydrogenase isoenzyme 1 in serum and tumor tissue of a patient with small-cell carcinoma

Histological examination of supraclavicular lymph node tissue obtained at biopsy from a 63-year-old man disclosed metastatic small-cell carcinoma. On admission and for four days subsequently, total lactate dehydrogenase (LD; EC 1.1.1.27) activity in serum was 6.5 times normal; studies of LD isoenzyme showed persistently increased LD-1, with LD-1 greater than LD-2. Isoenzyme electrophoresis of tissue homogenates prepared from the patient's tumor also showed the LD-1 greater than LD-2 pattern. Isoenzyme studies for supraclavicular lymph node tissue from five control subjects showed contrasting isoenzyme patterns as compared with the patients in whom LD-2, LD-3, and LD-4 predominated. Because these abnormalities were persistent, they differ from the temporal sequence for LD usually seen in myocardial infarction. This emphasizes the importance of repetitive sampling for clinical interpretation of data on this enzyme.     

Atypical patterns of lactate dehydrogenase isoenzymes in acute myocardial infarction

Total lactate dehydrogenase (LD; EC 1.1.1.27) activity in serum and LD isoenzymes were quantified in 190 patients with acute myocardial infarction (AMI) 24, 48, and 72 h after admission. In 90% of the 570 blood specimens an LD isoenzyme pattern typical of AMI (LD-1/LD-2 greater than 0.76) was found. The other 56 blood specimens showed an LD isoenzyme pattern atypical of AMI (LD-1/LD-2 less than 0.76). They were divided into three groups: 28 specimens with isomorphic pattern (relative increase in all five LD isoenzymes); 18 with relatively increased LD-3 proportion (greater than 35%); and 10 specimens with increased LD-5 proportion (greater than 10%). No difference was found in mean total LD activity in serum between the typical isoenzyme group and the three atypical groups. The LD isomorphic pattern was found in 60% of AMI patients complicated by cardiogenic shock. Fifty percent of AMI patients admitted with pulmonary edema showed increased LD-3 proportion and half of the patients with AMI and congestive heart failure, predominant right, demonstrated increased LD-5 proportion. We conclude that although most patients with AMI present at diagnosis with a typical LD isoenzyme pattern, it is important to recognize that some may present with atypical LD isoenzyme patterns, which may be associated with specific AMI complications.     

Two methods compared for measuring LD-1/total LD activity in serum

We present evidence for the utility of an improved assay for the activity of lactate dehydrogenase (EC 1.1.1.27) isoenzymes 1 and 2 in serum, involving inhibition of the H-subunit of LD by pyruvate at pH 7.1. Results correlate well with the LD-1/total LD ratio as evaluated by immunological assay and, as an index to infarct, the method is superior to either the change in CK-MB activity or to the LD-1 activity or to a combination of these tests, as is the percentage of LD-1 to total LD activity. Moreover, the percentage inhibition of LD activity by pyruvate may have an advantage over other methods of isoenzyme fractionation because of its smaller population CV for patients with acute myocardial infarction than is true of other methods. We also demonstrate how, using a linear discriminant analysis, we compared this method with alternative methods. We determined that evaluation of CK-MB isoenzyme contributes no information in addition to that obtained from the LD-1 isoenzyme.     

Hepatic infarction: biochemical study of a case

Hepatic infarction was observed post mortem in a 27-year-old man who died of aortic dissection. Blood had been sampled at admission and 12 and 19 hours later. Values for aspartate aminotransferase and alanine aminotransferase in serum were markedly above normal, whereas those for alkaline phosphatase and gamma-glutamyltransferase were only marginally increased. A threefold-increased creatine kinase was ascribable solely to isoenzyme CK-3, suggesting muscle breakdown. Moreover, total lactate dehydrogenase activity was increased threefold, accounted for by a ninefold increase in LD-5 isoenzyme. Those enzyme activities in serum that evidently are associated with acute hepatocellular necrosis increase quickly in hepatic infarction, and CK isoenzyme assay is a useful adjunct if LD-5 increases are significant.     

Lactate dehydrogenase isoenzyme-1/total ratio: accurate for determining the existence of myocardial infarction

We have gradually revised our medical protocols for measuring creatine kinase MB isoenzyme (CK-MB) and lactate dehydrogenase isoenzyme-1 (LD-1) because of identifiable problems in the use of an interpretation of CK-MB isoenzyme associated with slowly evolving or small myocardial infarct, the use of thrombolytic therapy, or burn and trauma, each of which affects the rate of appearance and composition of isoenzymes present. Despite recent evidence of the efficacy of LD-1 isoenzyme measurement in the first 12 to 24 h of myocardial infarction, this test is not widely used because of overstated assumptions about the value of CK-MB. Here we studied the adequacy of the current isoenzyme assays by determining the value of CK-MB and LD-1 at optimum serum sampling times and establishing the contribution of individual and combined predictors to diagnostic efficiency. We conclude that the LD-1/total LD activity ratio in serum is superior to measurement of CK-MB or LD-1, or both, in the diagnosis of acute myocardial infarction. Moreover, this ratio is most valuable when interpretation of the result for CK-MB isoenzyme is equivocal in patients with small or evolving myocardial infarcts.     

Determination, by radioimmunoassay, of the mass of lactate dehydrogenase isoenzyme 1 in human serum and of its rate of removal from serum after a myocardial infarction

In this radioimmunoassay of lactate dehydrogenase-1 (LD-1; EC 1.1.1.27) in human serum we use a commercial LD-1-selective assay system and a goat antiserum. We have determined the fractional rate of disappearance from serum and the half-life of LD-1, in terms of both enzyme activity and enzyme mass, in 21 myocardial infarction patients. Our evidence suggests that this isoenzyme is inactivated in serum. Furthermore, our data suggest that the conventionally accepted half-life of about 110 h for serum LD-1 activity may grossly overestimate the actual LD-1 half-life in many post-myocardial infarction patients.     

Lactate dehydrogenase isoenzymes in serum during recent acute myocardial infarction

Lactate dehydrogenase (LD, EC 1.1.1.27) isoenzymes 1 and 2 and the LD 1:2 ratio were determined in 62 patients with recent myocardial infarction 24, 48, and 72 h after total serum LD activity had returned to normal values. From the results we could define two groups of patients. The first, 40 patients in whom proportions of LD-1 and LD-2 isoenzymes in serum and the LD 1:2 ratio were all within the normal reference interval, all had an uncomplicated course of recovery from myocardial infarction. In the remaining 22 patients, LD-1 still exceeded LD-2 24 to 72 h after total LD activity returned to normal values; i.e., the ratio was similar to that in patients with myocardial infarction. Seven of these 22 patients (32%) had a complicated course, with re-infarction in all seven. Thus, even in the presence of normal total LD activity, a high LD 1:2 ratio may reflect a consistent focal myocardial necrosis in some patients with recent myocardial infarction and may serve as an early marker for further re-infarction.     

Improved column method for separating lactate dehydrogenase isoenzymes 1 and 2

Lactate dehydrogenase (LD) isoenzymes 1 and 2 in human serum were separated on a column of diethylaminoethyl-Sephadex. Samples layered on mini-columns were eluted with buffered sodium chloride (100, 150, and 200 mmol/liter). Lactate dehydrogenase activity in column effluents was measured by the Wacker method, and their isoenzyme content was evaluated by electrophoresis on polyacrylamide gel. Results for column-fractionated LD-1 and LD-2 were expressed in two ways: LD-1/LD-2 ratios and total LD-1 + LD-2 activities. The former is a more specific indicator of myocardial infarction than the latter. Sera from 10 patients with acute myocardial infarction (increased creatine kinease isoenzyme MB activity) exhibited ratios in the range of 0.92 to 1.56, ratios for 10 patients without heart disease (normal creatine kinase MB) ranged from 0.33 to 0.69.     

Isoforms of creatine kinase isoenzymes in serum in acute myocardial infarction after intracoronary thrombolysis

Kinetics of the catalytic activities of creatine kinase (CK;EC 2.7.3.2) for three CK-3 and two CK-2 isoforms in serum were studied in 20 patients with myocardial infarction randomly assigned to receive either intracoronary urokinase (group A) or conventional therapy (group B). The temporal characteristics of isoform changes described were (a) time at which the isoform activities are significantly greater than initial values, (b) maximal rate (Ka) at which isoforms are released into blood, (c) time lag from onset of pain until maximum activity value, (d) peak value of each serum isoform, and (e) rate (Kd) at which each isoform is cleared from serum. Thrombolytic treatment induced earlier peak times in group A: for CK-3(3), 7.4 vs 20.0 h; for CK-3(2), 11.6 vs 24.8; for CK-3(1), 18.6 vs 34.3; for CK-2(2), 9.1 vs 17.8; and for CK-2(1), 11.8 vs 26.8 (numbers given are medians; for all isoforms, P less than 0.05). Ka values were at least twofold greater and the first increase was significantly earlier in the urokinase group. Consequently, the ratio for CK-3(3) to CK-3(1) activities peaked significantly earlier in group A. Isoform peak activities and Kd were not significantly different between the two groups.     

Increased activities of creatine kinase and lactate dehydrogenase isoenzymes in a patient with metastatic ovarian tumor

A 50-year-old woman with metastatic rhabdomyosarcoma of the ovary had increased activities of creatine kinase (CK; EC 2.7.3.2), CK-MB isoenzyme, lactate dehydrogenase (LD; EC 1.1.1.27), and LD-2 isoenzyme in her serum. The isoenzyme activities did not show a pattern of increasing, then decreasing. Clinical findings, including electrocardiograms, did not support the diagnosis of myocardial infarction. We suggest that high activities of CK-MB and LD-2 in serum may serve as a marker of rhabdomyosarcoma.     

Lactate dehydrogenase isoenzymes in serum during unstable angina

Values for total lactate dehydrogenase (LD, EC 1.1.1.27) activity in serum, LD isoenzymes 1 and 2, and the LD 1:2 ratio in 25 patients with unstable angina were compared with the same variables in 25 patients whose angina was stable 24, 48, and 72 h after admission. Mean total LD activity and mean LD-2 activity were found to be within the normal range, both in the unstable angina and stable angina groups of patients. In the unstable angina group the mean LD-1 was significantly higher (p less than 0.01) than in the stable angina group at each time studied. The mean LD 1:2 ratio was also significantly different (p less than 0.001) between the two groups of patients. In the unstable angina group of patients the ratio was increased (0.85, SD 0.09), as in patients with acute myocardial infarction, whereas in the stable angina group of patients the ratio was normal (0.60, SD 0.06). We conclude that a high LD 1:2 ratio, even in the presence of normal total LD activity, may indicate myocardial damage in some patients with unstable angina and could therefore help in the clinical and functional evaluation of patients with unstable angina.     

Selective determination of lactate dehydrogenase isoenzyme 1 in serum after inhibition by 1,6-hexanediol

A rapid selective method for measuring the activity of lactate dehydrogenase isoenzyme LD-1 in serum by using 1,6-hexanediol as an inhibitor of the M-subunit was developed. Hexanediol was added to serum at a final concentration of 0.7 mol/l. After incubation at 30 degrees C for 15 min, the activity was measured with an automatic analyser. The inter-assay coefficient of variation was 6.9% for the lactate dehydrogenase isoenzyme LD-1 measurement. The results obtained from the sera of 100 patients analysed by the proposed selective method and by the conventional electrophoretic method, respectively, showed an excellent correlation. This selective method was used to determine the lactate dehydrogenase isoenzyme LD-1 activity of sera from patients with acute myocardial infarction, and the results were correlated well with those obtained by the immunological, Roch Isomune method. Addition of 1,6-hexanediol did not affect the measurement of activities of other enzymes such as alkaline phosphatase, gamma-glutamyltransferase, aspartate aminotransferase and alanine aminotransferase.     

Lactate dehydrogenase isoenzyme 1: Its usefulness as a screening test in diagnosis of myocardial infarction

Immunological assay of LD-1 activity provides a quantitative measurement of the type of lactate dehydrogenase (LD, EC 1.1.1.27) activity characteristic of myocardial origin. Using this test, a laboratory diagnosis of myocardial infarction can be either ruled out or confirmed in approximately 75% of patients in whom this diagnosis is suspected, without electrophoretic separation of creatine kinase (CK, EC 2.7.3.2.) and LD isoenzymes. Normal total CK and LD activities cannot be used to rule out myocardial infarction since CK-MB and LD-1 may have increased although total activities remain within their reference ranges. LD-1 activity increases as quickly as CK-MB following the onset of pain in the majority of patients but it remains elevated longer giving a greater period of time during which the diagnosis of myocardial infarction can be confirmed.     

Time-related changes in the diagnostic utility of total lactate dehydrogenase, lactate dehydrogenase isoenzyme-1, and two lactate dehydrogenase isoenzyme-1 ratios in serum after myocardial infarction

Using receiver-operating characteristic (ROC) curve and likelihood ratio analysis, we examined the diagnostic utility of total lactate dehydrogenase (LD; EC 1.1.1.27) activity (I). LD isoenzyme-1 activity (II), and the LD-1 percentage of total LD activity (III), LD-1 LD-2 (IV), and LD-1/LD-4 (V) in 347 persons admitted to the Cardiac Care Unit (of whom 173 were subsequently proven to have had myocardial infarction). Blood was sampled from these subjects at about 6-h intervals for up to 96 h from the onset of chest pain. Defining an "effective" test as one having an area under the ROC curve of greater than or equal to 0.9, we determined the ranked utility (greatest to least) of these tests as V = IV greater than III greater than II greater than I. Tests III, IV, and V had by this criterion, diagnostic effectiveness equivalent to measurements of creatine kinase-2 in serum but in samples obtained at later time intervals. The decision thresholds for both high (constant) test sensitivity and specificity varied with time, to differing extents, over the entire 96-h period, a finding with important diagnostic implications. We document positive and negative likelihood ratio values for each of these tests throughout the entire period of study.     

"Flipped" patterns of lactate dehydrogenase isoenzymes in serum of elite college basketball players

We kinetically measured total lactate dehydrogenase (LD, EC 1.1.1.27), total creatine kinase (CK, EC 2.7.3.2), and aspartate aminotransferase (AST, EC 2.6.1.1.) in 16 elite college basketball players, before the competition season and not in close temporal relation to near-maximal exercise, and in 17 healthy non-athlete controls. LD isoenzymes were determined by both electrophoretic and immunoprecipitation methods. CK-MB isoenzyme was measured electrophoretically. We found significantly higher mean LD-1 values and LD-1/LD-2 ratios in the players than the controls: 31.6 (SD 3.7)% vs 25.8 (SD 3.2)% (P less than 0.005) and 1.1 (SD 0.13) vs 0.87 (SD 0.16) (P less than 0.001), respectively. A "flipped" LD pattern (LD-1 greater than LD-2) was found in half the players and in six of the eight black athletes, but in only two of the control group and in none of the black controls. Mean CK activity in serum exceeded normal values in the serum of the athletes and was higher in comparison with the control group [274 (SD 156) vs 103 (SD 82) U/L]. Mean CK was significantly higher in the eight athletes with the flipped LD pattern than in those with LD-1 less than LD-2 [322 (SD 163) vs 180 (SD 98) U/L; P = 0.05], and also in comparison with CK in the two controls with flipped LD pattern. We saw no significant difference in mean CK between the nine players with normal immunochemical LD-1/LD ratios and the seven players with above-normal ratios. CK-MB was not detected in either athletes or controls. None of the players had any clinical or electrocardiographic evidence for myocardial ischemia or infarction. Evidently the flipped LD pattern usually found in patients with acute myocardial infarction and reported in some athletes after extreme exercise such as ultra-marathon running may also be found in athletes who are in their "basal fitness shape" but who are not involved in competitive physical activity.     

IgA-CK-BB complex with CK-MB electrophoretic mobility can lead to erroneous diagnosis of acute myocardial infarction

This patient, on admission, presented with a tentative diagnosis of myocardial infarction: the electrocardiogram showed a nonspecific ST-segment and T-wave abnormalities, and total creatine kinase (CK; EC 2.7.3.2) activity was slightly increased (238 U/L). However, a high electrophoretic value for CK-MB (50% of total CK activity) and the electrophoretic pattern of lactate dehydrogenase (EC 1.1.1.27) isoenzymes ruled out myocardial infarction. The isoenzyme migrating as CK-MB was found later to contain no immunologically normal CK-M subunits, and it was bound to IgA. A mixture of the patient's serum and a human serum control containing all CK isoenzymes showed altered electrophoretic mobility only for CK-BB, indicating that the patient's serum contained antibodies to the B unit of CK. Elution from a Sephadex G-200 column showed that the peak at which most of the anodic CK was eluted corresponded to a molecular mass of approximately 200 kDa. Evidently this atypical isoenzyme was an IgA-CK-BB complex. Because this macro CK type 1 can mimic CK-MB, it may therefore be a source of confusion.     

Serum isoforms of creatine kinase isoenzymes

The CK-2 and CK-3 isoenzymes of human serum creatine kinase (CK) can be further subdivided into five isoforms (subforms derived from the same isoenzyme). Three are derived from CK-3 and two from CK-2. The formation of these isoforms is a postsynthetic phenomenon brought about by a serum carboxypeptidase that acts on the M monomer of the enzyme. Sera from healthy subjects contain CK-3(1) as the dominant isoform with lesser amounts of CK-3(2) and CK-3(3). Following damage of muscle tissue, the serum isoform distribution changes as a result of the increased release of CK enzyme. This provides more diagnostic information concerning acute myocardial infarction and other muscle diseases than is available from routine CK isoenzyme analysis.     

Diagnostic efficiency of lactate dehydrogenase isoenzymes in serum after acute myocardial infarction

Diagnostic efficiency of lactate dehydrogenase isoenzymes were studied in 117 consecutive patients admitted with some symptoms of acute myocardial infarction. The results of lactate dehydrogenase isoenzyme tests were not available to the physicians, who diagnosed the patients according to criteria based on clinical symptoms, electrocardiographic findings and changes in three serum enzymes. Acute myocardial infarction was diagnosed in 41 patients. The diagnostic efficiency of lactate dehydrogenase isoenzyme 1 and the various ratios between this and the other isoenzymes were compared using receiver operating characteristic curves and logistic discriminant analysis. Lactate dehydrogenase isoenzyme 1 was the best parameter on the second day after admission. On that day, calculating the various ratios between isoenzyme 1 and the other isoenzymes did not improve discrimination.