From the Guidelines
Elevated lactate dehydrogenase (LDH) levels are a non-specific marker of infection, and in the context of pleural infection, an LDH level above 1000 IU/l indicates a complicated parapneumonic effusion or empyema, requiring chest tube drainage. During infections, LDH levels often increase due to tissue damage and cellular destruction caused by pathogens or the immune response 1. This enzyme is released when cell membranes are damaged, making it a marker of cell injury rather than a specific indicator of infection type. LDH is particularly elevated in certain infections like Pneumocystis jirovecii pneumonia (PJP), where levels can exceed 400-500 U/L and correlate with disease severity. Other infections associated with significant LDH elevation include severe COVID-19, bacterial pneumonia, tuberculosis, and various viral infections.
When evaluating a patient with suspected infection and elevated LDH, additional specific tests are necessary for diagnosis, including cultures, PCR testing, or imaging studies. The degree of LDH elevation may help assess infection severity and treatment response, with decreasing levels often indicating clinical improvement. However, since LDH can also be elevated in non-infectious conditions like malignancies, hemolysis, and tissue injury, clinical context is essential for proper interpretation. In the context of pleural infection, the British Thoracic Society guidelines suggest that an LDH level above 1000 IU/l is indicative of a complicated parapneumonic effusion or empyema, which requires chest tube drainage 1.
Some key points to consider when evaluating LDH levels in the context of infection include:
- LDH levels can be elevated in a variety of non-infectious conditions, making clinical context essential for proper interpretation 1
- The degree of LDH elevation can help assess infection severity and treatment response 1
- Additional specific tests, such as cultures, PCR testing, or imaging studies, are necessary for diagnosis when evaluating a patient with suspected infection and elevated LDH 1
- In the context of pleural infection, an LDH level above 1000 IU/l indicates a complicated parapneumonic effusion or empyema, requiring chest tube drainage 1
From the Research
LDH and Infection
- LDH levels are commonly elevated in patients with infections, particularly in those with Pneumocystis carinii pneumonia (PCP) 2.
- The relationship between LDH levels and radiographic severity of pneumonia has been studied, with results showing that LDH levels reflect the degree of radiographic abnormality and are elevated in both PCP and non-PCP pneumonia 2.
- Other studies have investigated the use of antibiotics, such as piperacillin/tazobactam, in the treatment of bacterial infections, including hospital-acquired pneumonia 3, 4.
- The role of LDH as a therapeutic target and lactate as a potential marker for monitoring treatment response in inflammatory diseases, including COVID-19, has also been explored 5.
- Additionally, research has examined the association between serum LDH levels and selected opportunistic infections, as well as HIV progression, with findings suggesting that higher LDH levels are associated with certain infections and lower CD4+ lymphocyte counts 6.
Key Findings
- Elevated LDH levels are associated with radiographic severity of pneumonia 2.
- Piperacillin/tazobactam is an effective treatment for patients with lower respiratory tract, intra-abdominal, urinary tract, gynaecological, and skin/soft tissue infections 3.
- LDH levels and lactate may serve as markers for monitoring treatment response in inflammatory diseases 5.
- Higher LDH levels are associated with certain opportunistic infections and lower CD4+ lymphocyte counts in HIV-infected patients 6.