Currently, the LTT is the only laboratory method to test for specific cellular sensitization.
First described in 1960, the test has evolved into a reproducible and highly sensitive method, taking advantage of the development in cell culture techniques and analytical methods.
Today its use extends beyond medical-biological research into routine diagnostic testing.
The test is based on the principle of antigen/allergen-specific induction of cell division in lymphocytes following contact with their “fitting” antigen.
A positive reaction in the LTT indicates the presence of antigen-specific lymphocytes (memory cells) in the patient’s blood.

Around the year 2000, the LTT's sensitivity was still comparatively low. In type IV allergy testing, the LTT was at best equal to the skin test, if not inferior.
In these early years, its specificity in infection diagnostic testing was of concern.
It was relatively low as the quality of the test antigens available at that time was poor.
Frequently they triggered weakly positive and thus inconclusive reactions, making the interpretation of the results difficult.
This has changed dramatically in recent years.
Today, the LTT technologies used in specialised immunological laboratories are very reliable and offer high sensitivity and specificity.

Advances in cell culture methods and media, the quality of allergens and antigens used for cell stimulation and, last but not least, the fundamentally improved measuring methods available today have all contributed to this development.
The liquid scintillation counters used in the past to measure 3H-thymidine activity have been replaced by advanced solid-phase β counters, not requiring any subsequent manipulation of cultured cells.
Furthermore, the LTT now uses so-called micro-culture techniques which by allowing multiple test runs greatly enhance the reliability of the results.
Adding genetically engineered interferon-α to the cell culture has contributed to the development of this micro-culture technique among other modifications (von Baehr et al, J. Immunol. Methods 2001; 251: 63-71).
With the introduction of this optimised LTT version into routine testing in 2005, the test’s sensitivity and specificity greatly improved, especially in comparison with the MELISA methods that were still used at that time.
The lymphocyte transformation test is a demanding laboratory technology requiring not only expensive modern laboratory equipment but also laboratory staff with great experience and diligence. With the LTT, only few steps of the process can be automated. Even in today’s age of modern technology, good old manual processing by experienced staff trained in cell culture techniques is at the heart of cell cultures.
In addition, the level of standardisation in the respective laboratory has a significant impact on the analytical quality, as has the way how the methods were established and validated for each task. For this reason, cell-based analytic methods should only be used by specialized laboratories and institutes focussed on this technologies where these methods are accredited according to DIN 15189 by the National Accreditation Body for the Federal Republic of Germany (DAkkS).
The lymphocyte transformation test was first accredited in accordance with DIN 15189 at the Institut für Medizinische Diagnostik as early as 2004.
In its currently available modern version, the lymphocyte transformation test has firmly established itself as a medical diagnostic testing method for various diseases.

1. Immunodeficiency
   Detection of deficiencies and functional impairments of the cellular immune system. See information.
2. Pathogens
   Detection of the activity of chronic, persistent infections based on pathogen-specific T cell response (Borrelia, Chlamydia, Yersinia, Giardia lamblia, Herpes viruses, among others). See information.
3. Type IV allergy
   Detection/exclusion of allergic sensitization of the cell-mediated type (type IV allergy) e.g. to medications, metals, acrylates, environmental pollutants, moulds or food allergens. See information.

The Institut für Medizinische Diagnostik offers the following LTT profiles:
Each of the antigens and allergens included in the profile can also be tested individually.