This is a medical question of type : exams and tests 
 How to diagnose Aplastic Anemia ? 
 Your doctor will diagnose aplastic anemia based on your medical and family histories, a physical exam, and test results.
                
Once your doctor knows the cause and severity of the condition, he or she can create a treatment plan for you.
                
Specialists Involved
                
If your primary care doctor thinks you have aplastic anemia, he or she may refer you to a hematologist. A hematologist is a doctor who specializes in treating blood diseases and disorders.
                
Medical and Family Histories
                
Your doctor may ask questions about your medical history, such as whether:
                
You've had anemia or a condition that can cause anemia
                
You have shortness of breath, dizziness, headaches, or other signs and symptoms of anemia
                
You've been exposed to certain toxins or medicines
                
You've had radiation or chemotherapy (treatments for cancer)
                
You've had infections or signs of infections, such as fever
                
You bruise or bleed easily
                
Your doctor also may ask whether any of your family members have had anemia or other blood disorders.
                
Physical Exam
                
Your doctor will do a physical exam to check for signs of aplastic anemia. He or she will try to find out how severe the disorder is and what's causing it.
                
The exam may include checking for pale or yellowish skin and signs of bleeding or infection. Your doctor may listen to your heart and lungs for abnormal heartbeats and breathing sounds. He or she also may feel your abdomen to check the size of your liver and feel your legs for swelling.
                
Diagnostic Tests
                
Many tests are used to diagnose aplastic anemia. These tests help:
                
Confirm a diagnosis of aplastic anemia, look for its cause, and find out how severe it is
                
Rule out other conditions that may cause similar symptoms
                
Check for paroxysmal nocturnal hemoglobinuria (PNH)
                
Complete Blood Count
                
Often, the first test used to diagnose aplastic anemia is a complete blood count (CBC). The CBC measures many parts of your blood.
                
This test checks your hemoglobin and hematocrit (hee-MAT-oh-crit) levels. Hemoglobin is an iron-rich protein in red blood cells. It carries oxygen to the body. Hematocrit is a measure of how much space red blood cells take up in your blood. A low level of hemoglobin or hematocrit is a sign of anemia.
                
The normal range of these levels varies in certain racial and ethnic populations. Your doctor can explain your test results to you.
                
The CBC also checks the number of red blood cells, white blood cells, and platelets in your blood. Abnormal results may be a sign of aplastic anemia, an infection, or another condition.
                
Finally, the CBC looks at mean corpuscular (kor-PUS-kyu-lar) volume (MCV). MCV is a measure of the average size of your red blood cells. The results may be a clue as to the cause of your anemia.
                
Reticulocyte Count
                
A reticulocyte (re-TIK-u-lo-site) count measures the number of young red blood cells in your blood. The test shows whether your bone marrow is making red blood cells at the correct rate. People who have aplastic anemia have low reticulocyte levels.
                
Bone Marrow Tests
                
Bone marrow tests show whether your bone marrow is healthy and making enough blood cells. The two bone marrow tests are aspiration (as-pi-RA-shun) and biopsy.
                
Bone marrow aspiration may be done to find out if and why your bone marrow isn't making enough blood cells. For this test, your doctor removes a small amount of bone marrow fluid through a needle. The sample is looked at under a microscope to check for faulty cells.
                
A bone marrow biopsy may be done at the same time as an aspiration or afterward. For this test, your doctor removes a small amount of bone marrow tissue through a needle.
                
The tissue is checked for the number and types of cells in the bone marrow. In aplastic anemia, the bone marrow has a lower than normal number of all three types of blood cells.
                
Other Tests
                
Other conditions can cause symptoms similar to those of aplastic anemia. Thus, other tests may be needed to rule out those conditions. These tests may include:
                
X ray, computed tomography (CT) scan, or an ultrasound imaging test. These tests can show enlarged lymph nodes in your abdomen. Enlarged lymph nodes may be a sign of blood cancer. Doctors also may use these tests to look at the kidneys and the bones in the arms and hands, which are sometimes abnormal in young people who have Fanconi anemia. This type of anemia can lead to aplastic anemia.
                
Chest x ray. This test creates pictures of the structures inside your chest, such as your heart, lungs, and blood vessels. A chest x ray may be used to rule out infections.
                
Liver tests and viral studies. These tests are used to check for liver diseases and viruses.
                
Tests that check vitamin B12 and folate levels in the blood. These tests can help rule out anemia caused by vitamin deficiency.
                
Your doctor also may recommend blood tests for PNH and to check your immune system for proteins called antibodies. (Antibodies in the immune system that attack your bone marrow cells may cause aplastic anemia.)