Comparing TSPOT assay results between an Elispot reader and manual counts

Area of Science:

• Immunology
• Infectious Diseases
• Diagnostic Assays

Background:

• The T-SPOT.TB (TSPOT) assay is an interferon-gamma release assay used for tuberculosis infection detection.
• TSPOT results can be determined using automated Elispot readers or manual counting by technicians.

Purpose of the Study:

• To compare the agreement between automated and manual reading methods for T-SPOT.TB assay results.
• To investigate factors influencing agreement between different TSPOT counting methodologies.

Main Methods:

• A comparative study involving 2481 US healthcare workers.
• Analysis of TSPOT results using Cohen's kappa coefficient for inter-rater agreement.
• Logistic regression to assess the contribution of selected variables.

Main Results:

• High agreement rates between automated and manual TSPOT readings were observed (92.3%–93.1%).
• Good overall inter-rater agreement was found (kappa = 0.71).
• Significant variability in agreement levels was noted between individual technicians and the automated reader.

Conclusions:

• Automated Elispot readers and manual counts demonstrate good agreement for TSPOT in low TB burden settings.
• Inter-observer variability among technicians may affect the interpretation of borderline TSPOT results.
• The lack of a gold standard for latent tuberculosis infection (LTBI) prevents definitive conclusions on the superiority of either reading method.