Laboratory diagnosis of trachoma: a collaborative study

Area of Science:

• Ophthalmology
• Microbiology
• Infectious Diseases

Background:

• Laboratory diagnosis of trachoma is crucial for disease control.
• Standardized diagnostic methods are needed for reliable trachoma assessment.
• Chlamydial infections, including trachoma, require accurate laboratory identification.

Purpose of the Study:

• To evaluate the reproducibility of a standardized complement fixation (CF) test for trachoma diagnosis.
• To compare the performance of CF testing with Giemsa staining and fluorescent antibody (FA) techniques.
• To assess the correlation of laboratory results with clinical signs of trachoma.

Main Methods:

• Collaborative study involving three laboratories.
• Standardized complement fixation (CF) test using chlamydial group antigen.
• Comparison of CF test results with routine laboratory reagents.
• Cytological examination of conjunctival scrapings using Giemsa staining and fluorescent antibody (FA) techniques.

Main Results:

• The standardized CF test showed over 95% agreement between laboratories and with routine reagents, indicating high reproducibility.
• CF test positivity was limited but correlated with clinical signs in hyperendemic areas.
• Giemsa staining correlated well with clinical activity but had lower positivity rates than the FA technique.
• FA technique results did not accurately reflect clinical intensity.

Conclusions:

• The standardized CF test is a reproducible method for laboratory diagnosis of trachoma.
• Giemsa staining is a useful method for assessing clinical activity in trachoma, potentially identifying heavily infected individuals.
• The FA technique may overestimate infection prevalence compared to clinical presentation.