Table 2:

Initial considerations that can be used to inform target product profiles for Chlamydia trachomatis serological assays

	Measuring infection	Measuring disease	For use in vaccine evaluation
Performance requirements	High sensitivity and specificity; ability to distinguish first from repeat infection; ability to measure recent infection; and lower precision than in vaccine studies would be sufficient for monitoring and surveillance applications	Ability to distinguish between complicated and uncomplicated infections; ability to identify disease-specific antigens or combinations of antigens or the magnitude of response associated with the disease; and high specificity for sequelae to prevent over investment in resource-poor environments arising from over estimation of the incidence of C trachomatis sequelae	Ability to quantify burden of infection and disease; high precision and high sensitivity for determining C trachomatis-naive status for trials and distinguishing between exposure and infection; to measure vaccine efficacy, availability of markers of tubal involvement, potentially in combination with other measures (eg, cellular markers, radiological measures); and markers of vaccine-induced immune response will depend on the mechanism of action of vaccine and will need to distinguish between vaccine-induced and natural responses
Dependencies	Appropriate collections of population-based sera	Appropriate collections of population-based sera to estimate disease incidence; and availability of reliable cases and controls with clear case definition to estimate population excess fraction	Vaccine trial design; and mechanism of action of vaccine candidate
Statistical methods	C trachomatis serological assay thresholds appropriate to the application and population; and relation between seroprevalence and cumulative or annual incidence should consider the impact of time since infection and repeat infections on Chlamydia trachomatis antibodies	C trachomatis serological assay thresholds appropriate to the application and population	C trachomatis serological assay thresholds appropriate to the application and population
Technical requirements	High throughput, low volume, and low resource use methods would be valued	High throughput, low volume, and low resource use methods for monitoring and surveillance applications; and should tolerate methods requiring higher specimen volume and operator intensive methods	Should tolerate methods requiring higher specimen volume, and operator intensive methods