Indirect Coombs Test
Hemograma completoÚltima revisión: 7 de abril de 2026. Enfoque de fuentes: contexto estándar de interpretación de laboratorio, material médico de referencia y orientación clínica o de salud pública cuando corresponde.
¿Qué es Indirect Coombs Test?
The indirect Coombs test, also known as the indirect antiglobulin test (IAT), detects free (unbound) antibodies circulating in the patient's serum or plasma that have the potential to bind to red blood cell (RBC) antigens. The test is performed by incubating the patient's serum with reagent red blood cells of known antigen composition. If antibodies in the serum bind to antigens on the reagent RBCs, subsequent addition of anti-human globulin (AHG) causes agglutination, indicating a positive result.
The IAT is fundamental to pretransfusion compatibility testing (crossmatching) and prenatal antibody screening. In the blood bank, it ensures that donor red blood cells are compatible with the recipient's serum before transfusion, preventing potentially fatal hemolytic transfusion reactions. In obstetrics, it screens pregnant women for clinically significant RBC alloantibodies—particularly anti-D (Rh) antibodies—that can cross the placenta and cause hemolytic disease of the fetus and newborn (HDFN). The IAT also plays a role in antibody identification panels when unexpected antibodies are detected.
Por qué importa
The indirect Coombs test is critical for safe blood transfusion and prenatal care. In transfusion medicine, a positive IAT (antibody screen) means the patient has developed alloantibodies against foreign RBC antigens, likely from prior transfusion or pregnancy. These antibodies must be identified so that antigen-negative blood can be provided, preventing hemolytic transfusion reactions. In pregnancy, detection of anti-D or other clinically significant antibodies allows monitoring and intervention (anti-D immunoglobulin, intrauterine transfusion) to prevent or manage hemolytic disease of the newborn.
Rangos de referencia normales
| Grupo | Rango | Unidad |
|---|---|---|
| Adults and children | Negative | (no agglutination) |
Los rangos de referencia pueden variar entre laboratorios. Compara siempre tus resultados con los rangos proporcionados por tu laboratorio.
Qué significan los niveles altos de IAT
Causas comunes
- RBC alloantibodies from prior transfusion (anti-K, anti-E, anti-Fy-a, anti-Jk-a, etc.)
- Anti-D antibodies in Rh-negative individuals sensitized by Rh-positive blood
- Naturally occurring antibodies (anti-A, anti-B in ABO system)
- Warm or cold autoantibodies reacting with screening cells
- Passively acquired antibodies (anti-D immunoglobulin, IVIG)
Posibles síntomas
- No direct symptoms from a positive IAT
- If antibodies cause hemolysis after transfusion: fever, chills, back pain, dark urine, hypotension
- In pregnancy: fetal anemia, hydrops fetalis, neonatal jaundice (due to HDFN)
Qué hacer: A positive IAT triggers antibody identification using panels of reagent red blood cells with known antigen profiles. Once the antibody specificity is determined, antigen-negative compatible blood is selected for transfusion. In pregnancy, antibody titers are monitored serially—rising titers (typically critical titer ≥16 for anti-D) prompt referral for fetal surveillance including middle cerebral artery Doppler ultrasound. Rh-negative women receive anti-D immunoglobulin prophylaxis at 28 weeks and after delivery of an Rh-positive infant.
Qué significan los niveles bajos de IAT
Causas comunes
- Normal result—no clinically significant RBC antibodies detected in serum
Posibles síntomas
- No symptoms associated with a negative IAT
Qué hacer: A negative IAT means no unexpected RBC antibodies were detected, and crossmatch-compatible blood can be issued for transfusion. In pregnancy, a negative antibody screen is reassuring but should be repeated at 28 weeks gestation and after delivery. Rh-negative women with a negative screen should still receive anti-D immunoglobulin prophylaxis.
¿Cuándo se recomienda la prueba de IAT?
- Pretransfusion compatibility testing (type and screen)
- Prenatal antibody screening at first visit and 28 weeks
- Evaluation after suspected hemolytic transfusion reaction
- Monitoring antibody titers in alloimmunized pregnancies
- Prior to Rh immunoglobulin administration
Preguntas frecuentes
Biomarcadores relacionados
Lectura relacionada
Condiciones
Referencias y enfoque de revisión
Las páginas del glosario de biomarcadores son explicaciones educativas y deben interpretarse junto con los rangos de referencia y comentarios proporcionados por tu laboratorio y tu profesional de salud. Para conocer nuestros estándares editoriales y proceso de revisión, consulta nuestra Política editorial y nuestro Proceso de revisión de contenido.
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Subir resultados de laboratorio →Aviso médico: Esta información es solo educativa y no sustituye el consejo, diagnóstico ni tratamiento médico profesional. Los rangos de referencia pueden variar entre laboratorios. Consulta siempre a tu profesional sanitario para interpretar tus resultados concretos.