Introduction Viral diseases are among the most widespread and impactful illnesses affecting public health. They require accurate and rapid diagnosis to limit their spread and initiate appropriate treatment. Serological tests play a pivotal role in medical laboratories by detecting antibodies or viral antigens, making them an essential tool in the diagnosis and monitoring of viral diseases. Concept of Serological Tests Serological tests are laboratory analyses performed on blood serum to detect the immune system’s response to viral infections. This is achieved by measuring antibody levels (IgM and IgG) or through the direct detection of viral antigens. Types of Antibodies and Their Diagnostic Significance • IgM: Indicates a recent or acute viral infection. • IgG: Indicates a past infection or acquired immunity resulting from infection or vaccination. Importance of Serological Tests in the Diagnosis of Viral Diseases The importance of these tests lies in: • Early diagnosis of viral diseases • Determining the stage of infection (recent or past) • Monitoring the immune response • Evaluating vaccine effectiveness • Supporting epidemiological studies Main Serological Tests Used 1. ELISA Test It is one of the most commonly used tests and is characterized by high accuracy and sensitivity in detecting antibodies and viral antigens. 2. Rapid Tests These are used for quick preliminary diagnosis, especially in emergency situations and epidemics. 3. Agglutination Tests They are used in some viral diseases to detect the reaction between antibodies and antigens. Role of Serological Tests in Diagnosing Certain Viral Diseases • Viral hepatitis (HBV, HCV) • Human Immunodeficiency Virus (HIV) • Measles and rubella • Coronavirus (SARS-CoV-2) Integration with Molecular Tests Despite the importance of serological tests, they complement but do not replace molecular tests such as PCR. Combining both methods is essential to obtain an accurate diagnosis, especially in the early stages of infection. Conclusion Serological tests are among the fundamental tools in diagnosing viral diseases, as they provide crucial information about infection status and immune response. Continuous advancements in serological techniques contribute to improving diagnostic accuracy and supporting public health efforts in combating viral diseases. Al-Mustaqbal University is the first university in Iraq Department of Medical Laboratory Techniques – First in the Iraqi National Ranking.