The biomarker Abnormal Protein Band 1 is part of a blood test called "Protein Electrophoresis". 

Protein electrophoresis is a test that measures specific proteins in the blood. The test separates proteins in the blood based on their electrical charge. The protein electrophoresis test is often used to find abnormal substances called M proteins (the M stands for "monoclonal").

The presence of M proteins can be a sign of a type of cancer called myeloma, or multiple myeloma. Myeloma affects white blood cells called plasma cells in the bone marrow. Protein electrophoresis also tests for other proteins and antibodies (immunoglobulins). 

If the electrophoresis testing found any evidence of M proteins, the estimated amount of the monoclonal protein would be reported in the different bands (1, 2, and 3). Most people with monoclonal protein in their blood will have just one kind (band), and it will be reported as "Abnormal protein band 1". But some have two types (bands), and in rare cases there are three types (bands).

When an abnormal protein (band or peak) is detected, additional tests are done to identify the type of protein (immunotyping).

A variety of conditions are related to M proteins:

MGUS (monoclonal gammopathy of undetermined significance). If you have this condition, you have both healthy plasma cells and abnormal ones. The abnormal plasma cells make M proteins that show up in your blood. Most of the time, MGUS doesn't cause any problems or symptoms. But for some people, MGUS turns into a harmful condition, such as multiple myeloma or lymphoma.

Smoldering multiple myeloma. This is the stage between MGUS and myeloma. There are more abnormal plasma cells and M proteins in the blood. Smoldering multiple myeloma usually doesn't cause any symptoms.

Multiple myeloma. When plasma cells are cancerous and grow out of control, it's called multiple myeloma. These cancer cells build up in the bone marrow and crowd out healthy cells. They also make M proteins. Higher levels of M protein in the blood can lead to complications.

Waldenstrom's macroglobulinemia. This cancer affects small lymphocytes (white blood cells). These cancerous cells make M proteins. A buildup of these proteins can thicken the blood and lead to symptoms, such as fatigue and weight loss.