From the Guidelines
Hemolysis labs are a set of blood tests that detect and measure the breakdown of red blood cells in the body, including complete blood count (CBC), reticulocyte count, lactate dehydrogenase (LDH), haptoglobin, bilirubin levels, peripheral blood smear, and direct antiglobulin test (DAT) 1. These tests are crucial in diagnosing conditions like hemolytic anemia, autoimmune disorders, infections, drug reactions, and inherited disorders such as sickle cell disease or thalassemia. When evaluating hemolysis, it is essential to consider the patient's clinical history, family history, and the time of last blood transfusion, along with the laboratory results 1. The pattern of abnormal results across these tests helps physicians determine whether hemolysis is occurring, its severity, and its underlying cause. Some key tests that may be included in the workup for hemolysis are:
- Blood chemistry
- CBC with evidence of anemia, macrocytosis, evidence of hemolysis on peripheral smear
- LDH, haptoglobin, bilirubin, reticulocyte count, and free hemoglobin
- DIC panel, which could include PT or INR or PTT, and infectious causes
- Autoimmune serology
- PNH screening
- Direct and indirect bilirubin, direct agglutinin test, and if no obvious cause, bone marrow analysis, and cytogenetic analysis to evaluate MDS
- Evaluation for viral or bacterial (mycoplasma etc) causes of hemolysis studies
- Protein electrophoresis and cryoglobulin analysis
- Workup for BM failure syndrome if refractory including B12, folate, copper, parvovirus, iron, and thyroid, infection
- Glucose-6-phosphate dehydrogenase level
- Evaluation of common drug causes (ribavirin, rifampin, dapsone, interferon, cephalosporins, penicillins, NSAIDs, quinine or quinidine, fludarabine, ciprofloxacin, lorazepam, and diclofenac)
- Assessment of methemaglobinemia 1. The most recent and highest quality study recommends a comprehensive approach to diagnosing hemolysis, including a combination of these tests to guide appropriate treatment and improve patient outcomes 1.
From the Research
Definition and Diagnosis of Hemolysis
- Hemolysis is the abnormal breakdown of circulating red blood cells (RBCs) and can present as a primary disorder or arise secondary to another disease process 2.
- The evaluation of pathologic hemolysis is heavily dependent on assays performed in the clinical laboratory, including hematology, blood bank/transfusion medicine, clinical chemistry, and immunology 2.
- Laboratory tests that confirm hemolysis include reticulocytosis, increased lactate dehydrogenase, increased unconjugated bilirubin, and decreased haptoglobin levels 3, 4.
Laboratory Investigation of Hemolysis
- The laboratory investigation of hemolysis involves a range of assays, including serum bilirubin, lactate dehydrogenase, and reticulocyte count 5, 3.
- The direct antiglobulin test is used to differentiate immune causes from non-immune causes of hemolysis 3, 4.
- A peripheral blood smear should be performed to identify abnormal red blood cell morphologies 3.
- Plasma free hemoglobin is a direct biomarker for hemolysis and has been associated with clinical complications such as pulmonary hypertension and death in patients with sickle cell disease 6.
Classification and Causes of Hemolytic Anemia
- Hemolytic diseases are classified into hemoglobinopathies, membranopathies, enzymopathies, immune-mediated anemias, and extrinsic non-immune causes 3.
- Extrinsic non-immune causes of hemolytic anemia include thrombotic microangiopathies, direct trauma, infections, systemic diseases, and oxidative insults 3.
- Medications can cause hemolytic anemia through several mechanisms, including immune-mediated destruction and oxidative damage 3.
- Hemolytic anemia can be chronic or life-threatening and should be part of the differential diagnosis for any normocytic or macrocytic anemia 3.