Are there any "markers of low immunity" in people without any genetic immune disease?

Question

Are there any blood or other tests that can reveal the immune status of people who have frequent infections but do not seem to have any genetic immunodeficiency disease?

Merck Manuals mentions many immune tests, including blood cell and immunoglobulin tests, but what could be a simple set of tests to check immune status in general?

Answer 1

Low immunity with frequent infections in adults without any genetic immunodeficiency disease can be due to:

• Genetic predisposition (Cureus)
• Old age (J Clin Invest)
• Excessive stress (Psychol Bull)
• Smoking (Oncotarget)
• Excessive alcohol drinking (Alcohol Research)
• Chronic conditions, such as malnutrition, low stomach acid, diabetes, kidney or liver disease, anemia, connective tissue disease, AIDS, cancer, etc. and anatomical abnormalities in the upper respiratory or gastrointestinal tract (ArupConsult)
• Long term treatment with medications, such as steroids (CDC.gov)

If suspected, chronic conditions need to be ruled out by relevant blood tests (complete blood count, vitamins, minerals, glucose, protein, liver panel, kidney tests, tumor markers), endoscopy, chest X-ray, etc.

According to Overview of Immune Assessment Tests, Military Strategies for Sustainment of Nutrition and Immune Function in the Field (NCBI Bookshelf, 1999), the basic blood tests to evaluate immune status include:

• Complete blood count (white and red blood cells and platelets), and specifically, lymphocytes and neutrophils
• C-reactive protein (CRP), a marker of inflammation
• Immunoglobulins IgG and IgM, indicators of immune status in the blood and other body fluids
• Immunoglobulin IgA, an indicator of immune status of the secretions of the lining of the respiratory, gastrointestinal and genitourinary tract.

Low levels of the mentioned markers speak for low immunity.

Here's an example of a comprehensive diagnostic algorithm to check immune status in adults.

I strongly suggest everyone who wants to check his/her immune status to ask a specialist - a conventional immunologist - who can judge which tests to do and properly explain them. I advise against testing by some random "alternative" laboratory.