Common Variable Immunodeficiency (CVID) is a primary immunodeficiency disorder affecting the immune system’s ability to produce protective antibodies. Individuals with CVID experience significantly low levels of immunoglobulins, which are proteins that identify and neutralize foreign invaders like bacteria and viruses. This condition is considered rare and chronic, leading to an increased susceptibility to various infections throughout life. It represents one of the more frequently diagnosed forms of primary immunodeficiency.
When to Suspect CVID
Healthcare providers consider a CVID diagnosis when a person experiences recurrent, severe, or unusual infections. These include infections of the respiratory tract, such as pneumonia, bronchitis, and sinusitis, which can become chronic and lead to lung damage like bronchiectasis. Gastrointestinal issues, including chronic diarrhea, weight loss, nausea, and abdominal pain, are also common symptoms that may raise suspicion. Skin infections and an enlarged spleen can occur. While some cases have a genetic component, a family history of similar immune problems can indicate a need for further investigation.
The Diagnostic Journey
The diagnostic process for CVID begins with a thorough clinical evaluation by a healthcare professional. This involves a detailed medical history, focusing on infection frequency, severity, and types, along with a physical examination to assess overall health and identify signs of immune dysfunction. Before a CVID diagnosis can be made, it is important to rule out other potential causes of low antibody levels, known as secondary hypogammaglobulinemia. Certain medications, kidney disease, or conditions causing protein loss from the intestines can mimic CVID by reducing immunoglobulin levels. Once these secondary causes have been excluded, a referral to a specialist, usually an immunologist, is made to confirm the diagnosis.
Essential Diagnostic Tests
Several laboratory tests are performed to gather evidence for a CVID diagnosis. Measuring serum immunoglobulin levels is a primary step, where doctors assess the concentrations of IgG, IgA, and IgM in the blood. A marked decrease in at least two of these immunoglobulin types is a characteristic finding in CVID. For example, a person might have significantly low IgG and IgA, or low levels of all three major immunoglobulins.
Another test evaluates the body’s ability to produce specific antibodies in response to vaccines. Individuals are given booster shots for common antigens like tetanus, diphtheria, or pneumococcal bacteria. A poor or absent antibody response to these vaccines is a strong indicator of CVID. This test shows whether the immune system can mount an effective defense against specific threats, even if overall immunoglobulin levels are low.
B-cell enumeration and subset analysis, performed using flow cytometry, provide further insights into immune cell populations. While the total number of B cells may be normal in CVID, these cells do not mature properly into plasma cells, which are responsible for producing antibodies. Abnormalities in the types or proportions of B-cell subsets can be present. Additional tests, such as serum protein electrophoresis, may be conducted to exclude other conditions that could affect immunoglobulin levels.
Interpreting the Results and Confirming CVID
Confirming a diagnosis of CVID involves synthesizing information from clinical symptoms, the exclusion of other conditions, and the specific laboratory test results. The diagnosis is not based on a single test but rather a comprehensive evaluation. The expertise of an immunologist is important in interpreting this complex array of data. They can differentiate CVID from other primary or secondary immune deficiencies and ensure that all criteria are met. This thorough approach helps ensure an accurate diagnosis. Once CVID is definitively diagnosed, individuals can begin appropriate management strategies to help mitigate the impact of the condition.