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Sexually Transmitted Diseases:
doi: 10.1097/OLQ.0b013e31819b8d3d
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Diagnostic Methodologies for Chlamydia Screening in Females Aged 15 to 25 Years From Private Insurance Claims Data in the United States, 2001 to 2005

Owusu-Edusei, Kwame Jr PhD; Bohm, Michele K. MPH; Kent, Charlotte K. PHD

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From the Division of STD Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia.

The findings and conclusions in this manuscript are those of the authors and do not necessarily represent the views of the Centers for Disease Control and Prevention (CDC). Mention of company names or products does not imply endorsement by CDC.

Correspondence: Kwame Owusu-Edusei, Jr., PhD, Division of STD Prevention, Centers for Disease Control and Prevention, 1600 Clifton Road MS E-80, Atlanta, GA. E-mail: Kowusuedusei@cdc.gov.

Received for publication August 22, 2008, and accepted January 7, 2009.

Untreated Chlamydial Infection Can Progress into serious sequelae including pelvic inflammatory disease, ectopic pregnancy, and tubal infertility.1–4 In view of the potential sequelae, routine screening for chlamydia is recommended.5–10 Identifying chlamydia is essential for effective control and prevention programs. However, the majority of chlamydial infections are asymptomatic requiring specific and periodic diagnostic tests for detection.11,12 In the United States, an estimated 2.8 million cases occur each year among youth,13 for whom reported incidence rates are highest.14,15 Diagnostic tests for detecting chlamydia have evolved over the last 2 decades with substantial technological improvements in sensitivity. The corollary to the improvement in sensitivity is the increased potential to detect low-organism loads associated with asymptomatic infections.16,17 The increased use of more sensitive tests and expanded screening resulted in increased number of reports of chlamydia and has consequently been used to explain, in part, recent national and local increases in the incidence of chlamydia.18 Previous studies on the trends and volume of diagnostic tests used survey data largely from public laboratories.16–21 However, very little is known about the trends and volume of chlamydia diagnostic tests using claims data. Results from analyzing medical claims data can complement existing knowledge by providing additional information on the use of diagnostic tests from the private sector’s perspective, including some insights into their respective billing patterns. Closer examination of claims data may also provide insight into trends in the chlamydia Health Plan Employer Data and Information Set (HEDIS) measure.

To monitor adherence to chlamydia screening guidelines, HEDIS designated 6 diagnostic tests used for chlamydia screening in 2000.22 Additionally, there are 2 tests that are not organism-specific but are sometimes used for chlamydia and gonorrhea and have been included in the set of codes for chlamydia screening by the American Medical Association.23 Later on, they were considered for inclusion in the HEDIS list if more information were provided.24 The recent attempt to address the inclusion of the nonspecific codes may be a way to adjust to the changes in the use of multiplex platforms that can detect both chlamydia and gonorrhea, and address changes to the associated reimbursement issues. However, the inconsistencies in the list of codes may result in substantial differences in estimated screening rates if different sets of codes are used.

We analyzed chlamydia diagnostic tests from a private insurance claims database for females aged 15 to 25 years from 2001 through 2005 for 2 purposes: (1) to describe trends in the chlamydia test volume by current procedural terminology (CPT) code, and (2) to compare estimates of HEDIS chlamydia screening rates using HEDIS-defined codes with expanded HEDIS test codes.

We used data from the MarketScan Database (MEDSTAT Group, Ann Arbor, MI) for 2001 through 2005. The MarketScan Database contains information on employment-based health insurance plans with at least 100 enrollees including large employers and health plans (MarketScan Database, The Medstat Group Inc., Ann Arbor, MI). Employer sponsored private health plans cover almost 60% of the United States population and estimates of analyses from the MarketScan administrative databases can be projected to represent that segment of the population.25

To analyze trends and volume of the diagnostic tests, we extracted claims for females aged 15 to 25 using all 8 codes presented in Table 1 from outpatient clinical encounters. Next, we used the pharmaceutical, outpatient, and inpatient clinical encounters to determine females aged 15 to 25 who accessed care and were continuously enrolled in each year (i.e., enrolled for a minimum of 300 member days). We then used the HEDIS criteria22 to determine the percent of female enrollees aged 15 to 25 that were estimated to be sexually active in the past 12 months. Finally, we determined those who had at least 1 claim for chlamydia test during the past 12 months using 2 sets of codes; the 6 specific HEDIS CPT codes and then repeated the analyses using 8 codes that included the 2 nonspecific codes (Table 1).

Table 1
Table 1
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Annual volumes and distribution for the diagnostic tests are presented in Figure 1. Generally, the overall volume of tests increased substantially every successive year from 33,000 to 179,000. This increase is largely due to the increase in the size of the database (i.e., the number of enrollees) over the years (MarketScan Database, The Medstat Group Inc. Ann Arbor, MI). From 2001 through 2005, the volume of direct probe (DP), amplified probe (nucleic acid amplification test (NAAT)), direct probe for multiple organisms (MODP and amplified probe for multiple organisms MONAAT) increased, whereas the other 5 stayed fairly stable over the 5-year period. Although NAAT began with a lower volume than DP in 2001, it increased over the years as the use of nucleic acid amplification tests became more common, eventually surpassing DP by the end of 2005. The frequency of NAAT was more than double that of DP at the end of 2005. Among the non-HEDIS tests, MODP was significantly higher (P < 0.01) than MONAAT in all the years. The proportion of amplified methods (NAAT and MONAAT) increased successively while the proportion of DP methods (DP and MODP) decreased successively over the 5-year period (Fig. 1). Chlamydia rapid test immunoassay with direct optical observation (IADOO) made up a relatively small proportion of the overall tests each year.

Figure 1
Figure 1
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Our results showed that 40% to 45% of those who accessed care each year were estimated to be sexually active. Of those estimated to be sexually active in each year, approximately 14%, 15%, 19%, 27%, and 30% had one or more claims for chlamydia test each year from 2001 through 2005, in that order. A χ2 test for trend in screening rates was significant (P < 0.0001), indicating an upward trend in screening rates over the period our analyses covered. When we repeated the analyses using all the 8 CPT codes, the estimated screening rates were higher, but not significantly different from the estimated screening rates when we used the 6 HEDIS codes.

We analyzed the volume and trend for chlamydia screening codes as well as the screening rates for sexually active females aged 15 to 25 using claims data. We found that the majority of tests performed were NAATs and the proportion of NAATs tests continued to increase over the years. Similar to an earlier study, the majority of the chlamydia tests performed in public health laboratories in the 2004 calendar year were NAAT.16 Also, as found in a California-based laboratory survey study from 1996 through 2003, the relative frequency of the amplified probe tests (NAAT and MONAAT) increased over the years, whereas the relative frequency of the other tests declined.17

Our results also showed that the estimated screening rates for sexually active females aged 15 to 25 using HEDIS criteria doubled from 2001 to 2005 (14%–30%). We found no significant difference when we compared HEDIS chlamydia screening rates using HEDIS-defined codes with expanded HEDIS test codes.

Our study is subject to the general limitations associated with using claims data to estimate screening rates, such as underrecording and changing codes. Nonetheless, the MarketScan database might be a useful tool for monitoring screening rates over time if the biases in these types of datasets are understood. One potential bias is changing test types over time and their inclusion or exclusion from the monitoring process. Our analyses have shown that including the 2 nonspecific codes does not result in significantly different screening rates when the HEDIS criteria for estimating screening rates are used. However, given the fact that the proportions of MONAAT and MODP continue to make up a considerable proportion of the tests used, it is important to address the nonspecificity concerns. Recent discussions regarding the inclusion of the nonspecific codes were designed to accommodate dual initial tests for both chlamydia and gonorrhea that may be followed by a more specific test.26 Consequently, HEDIS guidelines attempted to address this specificity issue by requiring additional documentation if that code is used for chlamydia screening.26 However, the required additional information is not yet available in the MarketScan database.

An earlier study that used the Medstat MarketScan database data for the 2001 calendar year, reported that over 85% of females tested for chlamydia were also tested for gonorrhea, which included the use of dual assays for testing both chlamydia and gonorrhea.27 Thus it is conceivable that the use of the nonspecific codes as initial tests that may be followed by a HEDIS designated test and/or as dual tests to detect both chlamydia and gonorrhea may be the reason why we did not find any significant difference in the estimated chlamydia screening rates when we included (or excluded) them in our analyses; the numerator was the number of patients and not the number of tests performed.

In conclusion, our study has demonstrated that the MarketScan database can be a useful data source for monitoring trends in chlamydia diagnostic tests to provide the private sector perspective on trends and volume of tests used. Second, our analyses have shown that there is no statistically significant difference in screening rates when the non-HEDIS CPT codes are excluded (or included) in estimating chlamydia screening rates using the HEDIS criteria. However, the estimated screening rates for each year in our study were lower than the rates reported by the National Committee for Quality Assurance Annual State of Health Care Report,28 which used similar criteria for determining screening rates although the age bracket was slightly different.16–25 Our results are comparable with estimates found in other studies for the same age category examined in our study, despite the notable nuances in the methods used in the other studies.29–34

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