Determining Prevalence of Chlamydia Infection Among Medicaid Managed Care Enrollees in New York State, Excluding New York City

Background:  The National Committee for Quality Assurance introduced the Healthcare Effectiveness Data and Information Set measure for Chlamydia screening in 2000.  The Chlamydia screening rate for women enrolled in Medicaid managed care (MMC) has been publically reported since 2002, however the prevalence of Chlamydia infection among the New York State MMC population is unknown.

Objectives:  The primary objective of this study was to determine the feasibility of linking Medicaid administrative data with STD surveillance and Chlamydia prevalence monitoring data systems to determine Chlamydia prevalence among a population of MMC enrollees.

Methods:  A deterministic record linkage process was conducted on a retrospective cohort of women eligible for Chlamydia screening using computer algorithms, each consisting of a different combination of the patient’s first and last name, sex, date of birth and date of visit.  Eligible women included those 16-25 years of age with an event reported in one of the three data sources in 2005 and 2006.

Results:  There were 51,805 MMC females eligible for Chlamydia screening with 41,569 tests performed by their MMC plan; 32,012 from STD surveillance and 12,312 from Chlamydia prevalence monitoring data sources, respectively, were available for linkage. The computer algorithm produced 2,617 links with 1,373 verified as true matches (883 MMC – surveillance; 490 MMC - prevalence matches). Of these 1,373 matches, 376 (27%) were tested outside their MMC plan. Adding these to the calculation, the estimated Chlamydia prevalence was 2.3% (947/41,945).

Conclusions:  Linkage of Medicaid managed care and STD program data indicates that screening coverage in MMC plans may underestimate true testing levels. Chlamydia prevalence appears to be low in this population.

Implications for Programs, Policy, and/or Research: The results are intended to inform quality improvement initiatives among Medicaid managed care providers and health plans about the importance of screening for Chlamydia infection.