Intravenous Immunoglobulin (IVIG) is a therapeutic product derived from human plasma, containing a concentrated collection of antibodies, primarily immunoglobulin G (IgG). These antibodies are sourced from thousands of healthy blood donors. IVIG therapy can significantly influence the results of routine blood tests.
Understanding Intravenous Immunoglobulin (IVIG)
Intravenous Immunoglobulin (IVIG) is a medication made from pooled human plasma, purified to contain a high concentration of antibodies, predominantly immunoglobulin G (IgG). These antibodies are crucial components of the immune system, designed to identify and neutralize foreign invaders like bacteria and viruses. Healthcare providers administer IVIG directly into a patient’s vein.
IVIG serves a dual purpose: it acts as a replacement therapy for individuals with weakened immune systems who cannot produce enough of their own antibodies, and it also functions as an immunomodulator. In immunodeficiencies, it provides passive immunity, helping the body fight off infections. For autoimmune and inflammatory conditions, IVIG helps regulate an overactive immune response by interacting with various immune cells and signaling pathways.
How IVIG Influences Common Blood Tests
IVIG therapy can impact the results of several common blood tests. The large amount of protein introduced during IVIG infusion directly affects laboratory measurements, including an increase in total protein levels in chemistry panels.
The presence of exogenous antibodies can interfere with various immunological assays. Serological tests for specific infections (e.g., HIV, Hepatitis C, Lyme disease) may show false positive or false negative results. Autoimmune antibody panels are also affected. Blood typing and cross-matching procedures become challenging due to the infused antibodies.
In a complete blood count (CBC), IVIG can lead to transient effects. Some patients experience temporary, mild anemia. IVIG can also cause red blood cells to clump together (agglutination), falsely elevating mean corpuscular volume (MCV) readings. IVIG can also influence white blood cell and platelet counts.
Specific Mechanisms of Interference
Substantial protein, primarily IgG, infused during IVIG therapy directly increases total protein concentration and specifically elevates gamma globulin levels, thereby altering the albumin-to-globulin (A/G) ratio.
Exogenous antibodies within IVIG are another key mechanism of interference. These antibodies bind to targets in laboratory assays, leading to inaccurate results. For example, in serological tests for infections, infused antibodies might react with test reagents, causing false positives, or they could mask true positive results.
IVIG infusions can temporarily affect blood volume. The expanded plasma volume might dilute blood components and impact analyte concentration. IVIG can induce red blood cell agglutination. This clumping can lead to erroneous measurements of red blood cell indices like MCV and complicate accurate blood typing by interfering with antigen-antibody reactions.
Interpreting Blood Work While on IVIG
Interpreting blood work for individuals receiving IVIG therapy requires careful consideration and collaboration between patients and healthcare providers. The timing of blood draws relative to IVIG infusion is important, as drawing blood immediately after an infusion might show transient elevations due to the recent influx of proteins. Healthcare providers may recommend specific timing for blood tests, often before the next scheduled infusion, to get a clearer picture of the patient’s baseline status.
Patients should always inform their doctors, nurses, and laboratory personnel about their IVIG treatment. This ensures laboratory staff can apply appropriate handling procedures or interpret results with knowledge of IVIG interference. Laboratory results must always be interpreted within the context of the patient’s clinical condition, symptoms, and treatment history.
Having baseline blood tests performed before starting IVIG therapy provides a valuable reference point for comparison. This allows healthcare providers to differentiate between changes caused by IVIG and those reflecting the patient’s underlying condition or other health issues. Many laboratories are aware of IVIG’s potential impact and may have specific protocols or flags for samples from patients on this therapy to aid accurate interpretation.