Introduction: Who Should Seek Diagnostic Testing

Primary myelofibrosis is often discovered unexpectedly during routine medical check-ups, as many people do not show symptoms in the early stages of the disease. This makes regular health examinations particularly important, especially for individuals over the age of 60, when this condition is most commonly diagnosed.^[1]

You should consider seeking diagnostic testing if you experience persistent symptoms that do not go away on their own. These warning signs include feeling extremely tired or weak without an obvious reason, experiencing shortness of breath during mild physical activity, or noticing pain or a feeling of fullness in the upper left part of your abdomen. Other symptoms that warrant medical attention include unexplained fever, night sweats severe enough to soak your clothing, unintentional weight loss, bone pain, easy bruising or bleeding, and frequent infections.^[2][3]

If your doctor finds an enlarged spleen during a physical examination, or if routine blood tests show abnormal blood cell counts, further diagnostic testing for myelofibrosis may be recommended. The spleen is an organ located in the upper left part of your abdomen, and when it becomes enlarged, it may create a sense of heaviness or discomfort in that area.^[4]

Diagnostic Methods for Identifying Primary Myelofibrosis

Physical Examination

The diagnostic process typically begins with a thorough physical examination by your healthcare professional. During this examination, your doctor will ask detailed questions about your symptoms and medical history. They will carefully examine your body, paying special attention to your abdomen. By gently pressing on different areas of your belly, your doctor can check for signs of an enlarged spleen or liver, which are common findings in people with myelofibrosis.^[9]

An enlarged spleen, medically called splenomegaly, is one of the hallmark features of myelofibrosis. The spleen normally filters abnormal blood cells from your bloodstream, but in myelofibrosis, it becomes overworked as blood cell production moves outside the bone marrow. This extra work causes the spleen to grow larger than normal, which your doctor can often feel during the physical exam.^[4]

Blood Tests

Blood tests are essential tools for diagnosing myelofibrosis and provide important information about how well your bone marrow is functioning. Your healthcare professional will take a sample of your blood and send it to a laboratory for detailed analysis.^[9]

The most common blood test used is called a complete blood count, or CBC. This test measures the numbers of different types of cells in your blood, including red blood cells, white blood cells, and platelets. In people with myelofibrosis, this test typically shows low numbers of red blood cells, a condition called anemia. The counts of white blood cells and platelets may be either higher or lower than expected, depending on the stage of the disease.^[9]

When laboratory technicians examine blood samples from people with myelofibrosis under a microscope, they often see abnormally shaped cells. Red blood cells may appear teardrop-shaped instead of their normal round form. They may also find immature blood cells in the bloodstream that should normally stay in the bone marrow, including nucleated red blood cells (normoblasts) and immature white blood cells called myelocytes. This pattern is referred to as leukoerythroblastosis.^[5]

Genetic Testing

Genetic testing plays a crucial role in diagnosing primary myelofibrosis and understanding what is causing the disease. Doctors now know that approximately 90% of people with myelofibrosis have specific genetic changes, or mutations, in their blood-forming cells. These mutations are not inherited from parents and cannot be passed to children; rather, they are acquired changes that occur during a person’s lifetime.^[6]

The three most important genes that are tested are JAK2, CALR, and MPL. About 50 to 60% of people with myelofibrosis have a mutation in the JAK2 gene, specifically a change called V617F. This mutation causes proteins in blood cells to send constant signals telling the cells to grow and divide, even when the body does not need more blood cells.^[3][6]

Another 23.5% of people with myelofibrosis have a mutation in a gene called CALR (calreticulin). This genetic marker was discovered in 2013 and has implications for understanding how the disease might progress and respond to treatment. Between 5 and 10% of patients have a mutation in the MPL gene, which affects the receptor for thrombopoietin, a substance that helps control the production of platelets and other blood cells.^[3][5]

About 10% of myelofibrosis patients do not have mutations in any of these three genes. This situation is sometimes called “triple-negative” primary myelofibrosis. In these cases, doctors may look for mutations in other genes such as TET2 or ASXL1.^[5][8]

Imaging Tests

Imaging tests create detailed pictures of the inside of your body and help doctors see whether your organs have changed in size or appearance. For myelofibrosis, imaging tests are used primarily to check whether your spleen and liver are enlarged and to look for signs that scar tissue has replaced healthy tissue in your bone marrow.^[9]

The most commonly used imaging tests for myelofibrosis are computerized tomography (CT) scans and magnetic resonance imaging (MRI) scans. A CT scan uses X-rays and computer technology to create cross-sectional images of your body. An MRI scan uses powerful magnets and radio waves to create detailed images of soft tissues. Both tests are painless, though you will need to lie still inside a large machine while the images are being taken.^[9]

These imaging tests help doctors measure the size of your spleen and monitor changes over time. The spleen size is an important indicator of disease activity and helps guide treatment decisions. In myelofibrosis, doctors often track whether the spleen volume decreases in response to treatment.^[9]

Bone Marrow Aspiration and Biopsy

A bone marrow examination is the most definitive test for diagnosing primary myelofibrosis. This procedure involves two related tests: bone marrow aspiration and bone marrow biopsy. Both are usually performed at the same time, typically from a spot in the back of your hip bone, also called the pelvis.^[9]

During bone marrow aspiration, your doctor uses a thin needle to remove a small amount of liquid bone marrow. A bone marrow biopsy removes a small piece of solid bone tissue along with the enclosed marrow. The area is numbed with local anesthetic before the procedure to minimize discomfort, though you may feel some pressure and brief pain when the samples are taken.^[9]

The bone marrow samples are sent to a laboratory where specialists examine them under a microscope. In primary myelofibrosis, the bone marrow shows characteristic features, most notably an increase in scar tissue called fibrosis. The bone marrow also typically shows abnormal growth and clustering of megakaryocytes, which are the cells that produce platelets.^[5]

The degree of fibrosis in the bone marrow is an important diagnostic finding. Specialists grade the fibrosis on a scale, and this grading helps distinguish between early-stage disease (sometimes called prefibrotic myelofibrosis) and more advanced overt myelofibrosis. The bone marrow biopsy is essential because fibrosis cannot be adequately assessed from blood tests or aspiration alone.^[5][6]

Distinguishing Primary from Secondary Myelofibrosis

It is important for doctors to determine whether myelofibrosis developed on its own (primary myelofibrosis) or as a progression of another blood condition (secondary myelofibrosis). Secondary myelofibrosis can develop when other myeloproliferative neoplasms such as polycythemia vera or essential thrombocythemia progress over time.^[3]

The manifestations of primary and secondary myelofibrosis are virtually identical, and treatment is generally the same for both. However, understanding your medical history and whether you were previously diagnosed with another blood disorder helps your doctor understand how your disease developed. This distinction is made by reviewing your past medical records, previous blood test results, and the timeline of when symptoms began.^[3]

Doctors must also rule out other conditions that can cause bone marrow fibrosis. Many different diseases can lead to increased scar tissue in the bone marrow, including certain cancers that have spread to the bones, some infections, autoimmune disorders, and exposure to certain chemicals or radiation. Thorough testing ensures that the diagnosis is accurate and that you receive the most appropriate treatment.^[5]

Diagnostics for Clinical Trial Qualification

Clinical trials are research studies that test new treatments or approaches to managing primary myelofibrosis. If you are considering participating in a clinical trial, you will need to undergo specific tests to determine whether you qualify for enrollment in the study.^[3]

The standard criteria for enrolling in myelofibrosis clinical trials typically include confirmation of the diagnosis through bone marrow biopsy showing the characteristic fibrosis pattern. Researchers need to verify that you truly have myelofibrosis rather than another condition. Most clinical trials also require genetic testing to identify whether you have mutations in the JAK2, CALR, or MPL genes, as some experimental treatments specifically target certain genetic changes.^[5][10]

Baseline blood tests are always required before joining a clinical trial. These tests establish your blood cell counts and other measurements at the start of the study, which allows researchers to track changes during treatment. Complete blood counts will document your red blood cell, white blood cell, and platelet levels. Additional blood tests may measure your liver and kidney function, as some treatments can affect these organs.^[9]

Imaging studies to measure spleen size are standard requirements for most myelofibrosis clinical trials. Researchers need a baseline measurement of your spleen volume using MRI or CT scans so they can determine whether the experimental treatment successfully reduces spleen size. Many trials set a minimum spleen size as an entry requirement, as treatments are often designed to help people with significantly enlarged spleens.^[13]

Some clinical trials use risk assessment tools to determine eligibility. One commonly used system is called the Dynamic International Prognostic Scoring System, or DIPSS. This scoring system considers factors such as your age, blood cell counts, presence of symptoms, and percentage of immature white blood cells in your blood. Patients are classified into risk categories such as low, intermediate, or high risk. Certain trials may only accept patients in specific risk categories.^[13]

Physical performance status is another consideration for trial enrollment. Researchers need to know whether you are able to care for yourself and engage in daily activities. This is typically measured using standardized scales that rate your level of functioning. Trials testing intensive treatments may require that you are relatively healthy aside from your myelofibrosis diagnosis.^[13]