Warm autoimmune haemolytic anaemia is diagnosed through a combination of blood tests and clinical examination that help identify the destruction of red blood cells and the antibodies responsible for this process. Understanding these diagnostic methods is essential for anyone experiencing symptoms such as unexplained tiredness, yellowing of the skin, or dark urine.

Introduction: Who Should Undergo Diagnostics

If you experience persistent tiredness, weakness, or dizziness that doesn’t improve with rest, it may be time to seek medical evaluation. These symptoms can indicate that your body is not receiving enough oxygen due to low red blood cell levels. Warm autoimmune haemolytic anaemia, often abbreviated as wAIHA, is a condition where your immune system mistakenly attacks your own red blood cells, and early diagnosis is crucial for proper management.^[1]

You should consider consulting a doctor if you notice yellowing of your skin or the whites of your eyes, a condition called jaundice. This happens because when red blood cells are destroyed, they release a substance called bilirubin that builds up in your body and causes this yellow discoloration. Other warning signs include darker than usual urine, rapid heartbeat, shortness of breath, or pale skin that persists beyond a few days.^[5]

People with existing autoimmune conditions such as lupus, rheumatoid arthritis, or thyroid disease should be particularly vigilant about these symptoms. Secondary wAIHA, which develops in connection with another underlying condition, accounts for about half of all cases. If you have blood cancers like lymphoma or chronic lymphocytic leukaemia, or if you’ve recently had a viral infection, your risk may be higher.^[1]

Women over the age of 40 are more commonly affected by this condition, though wAIHA can occur in anyone regardless of age or gender. If you fall into this demographic and notice the symptoms mentioned above, seeking prompt medical attention is advisable. The condition is rare, affecting only about 1 to 2 people per 100,000 each year, but it is highly manageable when caught early.^[1]

Diagnostic Methods for Identifying the Disease

The cornerstone of diagnosing warm autoimmune haemolytic anaemia is a blood test called the direct antiglobulin test, also known as the DAT or Coombs test. This test looks for antibodies that have attached themselves to the surface of your red blood cells. In warm autoimmune haemolytic anaemia, the test typically shows positive results for a type of antibody called IgG, and sometimes also for a protein called C3d.^[3]

When IgG antibodies attach to red blood cells at normal body temperature (around 37°C or 98.6°F), they mark these cells for destruction by your immune system. The direct antiglobulin test can detect these antibodies and confirm that an autoimmune process is occurring. However, in some rare cases, the test may yield false-negative results if the antibodies are of a different type, such as IgA, which standard testing reagents may not detect.^[6]

A complete blood count, or CBC, is another essential diagnostic tool. This test measures the levels of different types of blood cells in your body, including red blood cells. In wAIHA, you’ll typically have a low haemoglobin level, which is the protein in red blood cells that carries oxygen. Normal haemoglobin levels are generally around 12-16 grams per decilitre for women and 14-18 for men, but in wAIHA, these levels can drop significantly, sometimes below 7 grams per decilitre in severe cases.^[14]

Doctors also look at your reticulocyte count, which measures young red blood cells in your bloodstream. When your body is destroying red blood cells rapidly, your bone marrow tries to compensate by producing more cells. This leads to an elevated reticulocyte count, often above 2% of total red blood cells. A high reticulocyte count, combined with low haemoglobin, suggests that red blood cells are being destroyed faster than they can be replaced.^[14]

A peripheral blood smear involves examining your blood under a microscope. In wAIHA, the laboratory specialist will often see spherocytes, which are red blood cells that have lost their normal disc shape and become smaller and rounder. This happens because parts of the cell membrane are removed when antibody-coated cells pass through the spleen. The presence of spherocytes is a characteristic finding that supports the diagnosis of wAIHA.^[4]

Laboratory tests that measure the breakdown products of red blood cells provide additional diagnostic clues. Lactate dehydrogenase (LDH) is an enzyme released when cells are damaged or destroyed. In wAIHA, LDH levels in the blood are typically elevated, often above 500 international units per litre. Similarly, bilirubin, a yellow pigment produced when red blood cells break down, becomes elevated. You may see indirect or unconjugated bilirubin levels rising above the normal range of 0.2-1.0 milligrams per decilitre.^[14]

Another important marker is haptoglobin, a protein that binds to free haemoglobin released from destroyed red blood cells. In healthy individuals, haptoglobin levels range from 30 to 200 milligrams per decilitre. However, in wAIHA, these levels drop dramatically, often falling below 10 milligrams per decilitre, because the haptoglobin is being consumed as it binds to all the haemoglobin released from broken red blood cells.^[14]

Your doctor will also examine you for physical signs of the condition. An enlarged spleen, called splenomegaly, often develops in wAIHA because the spleen is working overtime to remove antibody-coated red blood cells from circulation. During a physical examination, your doctor may be able to feel your enlarged spleen below your left rib cage. Other physical findings include pale skin from anaemia and jaundice from elevated bilirubin levels.^[3]

It’s important to distinguish warm autoimmune haemolytic anaemia from cold autoimmune haemolytic anaemia, which is a different condition. In cold AIHA, the antibodies are of the IgM type and bind to red blood cells at cooler temperatures. The direct antiglobulin test in cold AIHA typically shows positive results for C3d but not IgG. This distinction matters because the two conditions require different treatment approaches.^[1]

Once wAIHA is diagnosed, your doctor will work to determine whether it is primary (occurring without an obvious cause) or secondary (related to another condition). This involves additional testing to look for underlying conditions such as autoimmune diseases, blood cancers, or viral infections. Blood tests for conditions like lupus or lymphoma, as well as reviewing your medication history, help identify potential secondary causes.^[5]

Diagnostics for Clinical Trial Qualification

Clinical trials investigating new treatments for warm autoimmune haemolytic anaemia use specific diagnostic criteria to ensure that enrolled patients truly have the condition and can safely participate. The direct antiglobulin test positive for IgG is typically the primary inclusion criterion. Trials usually require strong positive results, not borderline findings, to ensure accurate diagnosis of wAIHA rather than other forms of anaemia.^[14]

Most clinical trials establish minimum haemoglobin thresholds for enrolment. Patients often need to have haemoglobin levels below a certain point, commonly around 9 to 11 grams per decilitre, to demonstrate clinically significant anaemia. This ensures that the trial is testing the treatment in people who genuinely need intervention. However, trials also typically exclude patients with dangerously low haemoglobin levels, such as below 6 grams per decilitre, who may require immediate blood transfusion rather than experimental therapy.^[14]

Evidence of active haemolysis, which means ongoing destruction of red blood cells, is another standard requirement. This is demonstrated through elevated lactate dehydrogenase levels, decreased haptoglobin levels, and elevated indirect bilirubin. Clinical trials want to study patients whose disease is active rather than in remission, so these markers of red blood cell breakdown must be present at screening.^[14]

Reticulocyte counts are also important for trial qualification. An elevated reticulocyte count, often above 120,000 per microlitre or above 2% of total red blood cells, demonstrates that the bone marrow is responding appropriately to the anaemia by trying to produce more red blood cells. This helps distinguish wAIHA from conditions where the bone marrow itself is failing to produce adequate numbers of red blood cells.^[14]

Trials often require documentation that patients have tried and either failed to respond to or cannot tolerate standard treatments. This may include corticosteroids like prednisone, which are considered first-line therapy for wAIHA. Some trials specifically enrol patients who have relapsed after initial treatment success or who require ongoing high doses of steroids to maintain their haemoglobin levels.^[9]

Complete medical history and physical examination are essential parts of trial screening. Researchers need to document the duration of your illness, previous treatments and their outcomes, any side effects experienced, and whether your wAIHA is primary or secondary to another condition. Some trials may focus specifically on primary wAIHA, while others may include both primary and secondary cases. The presence of an enlarged spleen may also be documented as part of the baseline evaluation.^[14]

Baseline blood tests beyond those that diagnose wAIHA are typically required. These include comprehensive metabolic panels to check liver and kidney function, as many experimental treatments are processed through these organs. Complete blood counts that show not just red blood cell levels but also white blood cell and platelet counts help ensure that patients don’t have other blood disorders that could complicate trial participation or interpretation of results.^[14]

Some clinical trials may require testing to rule out other causes of haemolytic anaemia. This could include tests for inherited red blood cell defects, mechanical causes of red blood cell destruction, or medication-induced haemolysis. The goal is to ensure that participants truly have autoimmune haemolytic anaemia rather than another condition that might respond differently to the treatment being studied.^[12]

During the trial, participants undergo regular monitoring with the same diagnostic tests used for initial diagnosis. Haemoglobin levels, reticulocyte counts, lactate dehydrogenase, haptoglobin, and bilirubin are typically measured at scheduled intervals, often weekly or monthly depending on the trial design. This monitoring allows researchers to track whether the experimental treatment is working and to detect any safety concerns early.^[14]

Quality of life assessments and symptom questionnaires have become increasingly important components of clinical trial evaluation. Beyond measuring laboratory values, researchers want to understand whether treatments improve how patients actually feel. These assessments ask about fatigue levels, ability to perform daily activities, shortness of breath, and overall wellbeing. This patient-centred approach helps determine whether new treatments offer meaningful benefits beyond just changing blood test numbers.^[2]