Diagnostic utility of measuring lactate dehydrogenase levels and its isoenzyme activities for the evaluation of malignancy in feline pleural effusion and ascitic fluid

Lactate dehydrogenase (LDH) isoenzymes may be useful in the differential diagnosis of pleural effusion (PE) and ascitic fluid (AF) etiologies in cats since tissue damage induces their release, thereby changing the pattern of their activity. The present study aimed to determine the diagnostic utility of measuring LDH levels and its isoenzyme activities in PE or AF in cats with malignancy. We measured LDH levels and its isoenzyme activities in serum, PE, and AF in 29 cats and compared the results between malignant, infectious diseases, and non-malignant, non-infectious diseases. Receiver operating characteristic (ROC) analysis was performed to assess the accuracy of the tests in diagnosing feline malignancy. In PE or AF, significant differences were found in LDH levels and LDH isoenzymes activities among the three groups. The combination of LDH level and LDH-1 activity in PE or AF had the highest area under the ROC (AUC) value of 0.874 for discriminating malignant effusion from non-malignant effusion. The sensitivity and specificity of using the combination of LDH level (cutoff: <2,269 U/L) and LDH-1 activity (cutoff: <4.8%) in PE or AF for predicting malignancy with the highest AUC value were 94.4% and 72.7%, respectively. Our results suggest that the combination of LDH level and LDH-1 activity in PE or AF can potentially diagnose for malignancy. Considering that LDH isoenzymes can be measured inexpensively and easily, LDH tests can be readily accommodated in veterinary clinical practice.

Evaluation of Serum Levels of Lactate Dehydrogenase Isoenzymes in COVID- 19 Patients

Background: This study aimed to determine the serum levels of lactate dehydrogenase isoenzymes (LDH1, LDH2, LDH3, LDH4, and LDH5) and their contribution to the total lactate dehydrogenase enzyme elevation observed in COVID-19 patients. Design of study: This study was conducted in collaboration between Al-Nahrain University/College of Medicine/Chemistry and Biochemistry Department and Al- Yarmouk Teaching Hospital, Baghdad, Iraq. The study included 90 patients with confirmed COVID-19 infection: 45 with severe symptoms, and 45 with mild symptoms during the period from February 2021 to June 2021. The different LDH isoenzymes (LDH1, LDH2, LDH3, LDH4, and LDH5) were determined by enzyme-linked immunosorbent assay (ELISA) kits. Results: This study showed high correlation between total lactate dehydrogenase (LDH) enzyme and disease progression and severity in patients with COVID-19. The study also showed significantly higher levels of the lactate dehydrogenase isoenzymes (LDH1, LDH3, and LDH4) in patients with severe symptoms. Conclusion: This study suggests that elevation of serum lactate dehydrogenase (LDH) in patients with COVID-19 may be associated with the release of more than one of LDH isoenzymes into the bloodstream, therefore the use of total LDH as a specific biomarker for lung affectation in patients with COVID-19 is not specific, but the assay of all LDH isoenzymes could give a better understanding of the tissues most affected by the virus.

Clinical and Diagnostic Significance of Lactate Dehydrogenase and Its Isoenzymes in Animals

Lactate dehydrogenase (LDH) is widely distributed enzyme in cells of various living systems where it is involved in carbohydrate metabolism catalyzing interconversion of lactate and pyruvate with NAD+/NADH coenzyme system. Cells of tissues are direct source of lactate dehydrogenase isoenzymes that are naturally distributed in blood plasma/serum of animals and humans producing characteristic profile. This profile depends on intracellular isoenzyme concentration in all tissues that contribute to the common pool of lactate dehydrogenases in plasma/serum as a consequence of natural cell degradation. LDH is widely distributed in the body, high activities are found in the heart, liver, skeletal muscle, kidney, and erytrocytes, whereas lesser amounts are found in the lung, smooth muscle, and brain. Because of its widespread activities in numerous body tissues, LDH is elevated in a variety of disorders. There are many conditions that contribute to increased activity of LDH. An elevated total LDH value is a rather nonspecific finding. Therefore, LDH assays assume a more clinical significance when separated into isoenzyme fractions. The activity of LDH and its serum and tissue patterns and composition show great variations between the species. These differences do not allow using catalytic activities of LDH isoenzymes from one species to another. Instead, the pattern of serum LDH isoenzymes should be interpreted in respect to its species origin that is important in particular in veterinary medicine. Determination of total LDH activity and its isoenzyme pattern in serum of mammals had become one of the biochemical indicators in the assessment of organ disorders. When the content of cells is released from tissue to plasma, as on cell injury, the LDH isoenzyme pattern of the serum changes in favour of the profile of the affected organ (tissue) that can be used in the diagnostic practice.

A more universal and stable method for lactate dehydrogenase isoenzyme test

As an important enzyme for energy metabolism, lactate dehydrogenase (LDH) and its isoenzymes (LDH isoenzymes) have been extensively studied.