Predictors of repeat Chlamydia trachomatis infections diagnosed by DNA amplification testing among inner city females

OBJECTIVE

To describe the epidemiology of prevalent and incident chlamydia infection in order to assess the appropriate interval for chlamydia screening; and to identify risk factors predictive of infection and repeat infections.

DESIGN

Prospective longitudinal study of a consecutive sample of 3860 sexually active females aged 12-60 years tested for C. trachomatis by polymerase chain reaction in Baltimore City clinics during 11,904 patient visits over a 33 month period.

RESULTS

Chlamydia prevalence, incidence, and frequency to diagnosis of infection varied by age. Among 2073 females < 25 years, chlamydia infection was found in 31.2%. The median times to first and repeat incident infections were 7.0 months and 7.6 months, respectively. Among 1787 females > or = 25 years, chlamydia infection was found in 9.6%. Median times to first and repeat incident infections were 13.8 months and 11.0 months, respectively. Age < 25 years yielded the highest risk of infection.

CONCLUSIONS

Since a high burden of chlamydia was found among mostly asymptomatic females < 25 years in a spectrum of clinical settings, we recommend chlamydia screening for all sexually active females < 25 years at least twice yearly.

Geographic epidemiology of gonorrhea in Baltimore, Maryland, using a geographic information system

The epidemiology of gonorrhea is characterized by geographically defined hyperendemic areas, or "cores." Geographic information system (GIS) technology offers new opportunities to evaluate these patterns. The authors developed a GIS system linked to the disease surveillance database at the Baltimore Health Department and used this system to evaluate the geographic epidemiology of gonorrhea in Baltimore, Maryland, during 1994. There were 7,330 reported cases, of which 87.4% were in persons aged 15-39 years; 56.6% were of the cases were in males; and 60.5% of the cases were reported from the nonsexually transmitted disease (STD) clinic sector. Valid residential addresses were available for 6,831 (93.5%) of cases. In the GIS system, gonorrhea cases were geocoded by reported address using digitized maps, and assigned to census tract. Census tract-specific rates for persons aged 15-39 years were calculated using 1990 census data. Gonorrhea was reported from 196/202 (97%) of census tracts, of which 90 census tracts had >30 cases. For these 90 census tracts, rates were ranked. The core was considered as the top rate quartile, consisting of 13 geographically contiguous census tracts with rates 4,370-6,370 per 100,000; adjacent areas were 19 census tracts in the second quartile (rates: 3,730-4,370 per 100,000). As radial distance from the core areas increased, incidence rates decreased and male/female ratio increased, which is consistent with previous definitions of the core theory of STD transmission. Mapping of cases by provider showed that cases reported from STD clinics had similar geographic distribution to those from the non-STD clinic sector. From an operational perspective, GIS can be effectively integrated with clinical data systems to provide epidemiologic analysis.

Screening women for chlamydia trachomatis in family planning clinics: the cost-effectiveness of DNA amplification assays

BACKGROUND

Highly sensitive and specific DNA amplification assays are available for use on cervical and urine specimens. These new tests have the potential to identify more chlamydial infections than the commonly used enzyme immunoassay and DNA probe tests, yet they are more expensive. This study sought to assess the cost effectiveness of cell culture, enzyme immunoassay (EIA), DNA probe (Pace 2), polymerase chain reaction (PCR) of cervical and urine specimens, and ligase chain reaction (LCR) of cervical and urine specimens as screening tools for Chlamydia trachomatis in asymptomatic women younger than 30 years of age attending family planning clinics.

STUDY DESIGN

Program costs; medical cost savings of prevented sequelae in women, male sex partners, and infant; and number of prevented cases of pelvic inflammatory disease (PID), neonatal infections, and male sex partner urethritis and epididymitis were modeled in a decision analysis conducted from a health care system perspective. Results are expressed for a cohort of 18,000 women.

RESULTS

If no screening for C. trachomatis were conducted in Maryland, 497 cases of PID would develop, costing $2.2 million in future medical costs. Use of EIA to detect chlamydial infection would prevent 240 cases of PID and save $887,000 over no screening. Alternatively, use of DNA amplification assays on urine specimens would prevent up to an additional 66 cases and save $287,100 over EIA. Use of LCR on cervical specimens would prevent at least 13 additional cases of PID over the urine-based assays, but would cost $3,005 for each additional case prevented. In women receiving routine pelvic examinations, LCR of cervical specimens would prevent the most disease and provide the highest cost savings. In women not receiving routine pelvic examinations, use of LCR on cervical specimens would prevent the most disease but would cost approximately $28,000 per additional case of PID prevented over DNA amplification of urine.

CONCLUSIONS

Compared with EIA screening, the strategy with the lowest program costs, a screening strategy that combines use of DNA amplification on cervical specimens in women receiving pelvic examinations, and DNA amplification of urine in women with no medical indications necessitating a pelvic examination, prevents the most cases of PID and provides the highest cost savings. With enhanced sensitivity over the other diagnostic assays and with the use of noninvasive specimen collection, DNA amplification assays should be implemented as cost-effective components of a screening program for C. trachomatis.

Syphilis serology in human immunodeficiency virus infection: evidence for false-negative fluorescent treponemal testing

Injection drug users were assessed serologically for human immunodeficiency virus infection and syphilis every 6 months. Treatment histories were reviewed for any high-titer biologic false-positive (BFP) reactors, that is, persons with rapid plasma reagin (RPR) titers > or = 1:4 and negative results for fluorescent treponemal antibody absorption (FTA-ABS) tests. Selected sera were analyzed further by immunoblotting for the presence of antibodies reactive with specific Treponema pallidum antigens. Of 112 BFP reactors, 35 (31%) had at least one RPR test reactive at a dilution >1:8 while the FTA-ABS test remained nonreactive. Five reactors (4.5%) converted from nonreactive to reactive by FTA-ABS test; 4 (3.6%) were reactive by FTA-ABS tests but later became nonreactive. Antibodies to T. pallidum membrane antigens were detected in some samples that were persistently nonreactive by FTA-ABS test. Serologic patterns over time, along with very high-titer BFP reactions and reactivity with T. pallidum-specific antigens, suggest that some BFP reactions may represent FTA-negative syphilis.

Routine voluntary HIV screening in STD clinic clients: characterization of infected clients

Since January 25, 1988, the Baltimore City Health Department has offered routine, confidential, human immunodeficiency virus (HIV) testing to clients of the city's two sexually transmitted disease (STD) clinics. During the first 11 months of the program, testing was offered at 20,843 patient visits and was accepted at 15,181 (73%) of these; 612 (4%) individual clients had results that were positive for HIV. Four hundred thirty-seven (71%) seropositive clients returned for test results, post-test counseling, and further evaluation. Most HIV-infected clients were single, and black men accounted for 75% of seropositive individuals. HIV-infected women tended to be younger than infected men (7% of the female clients were adolescents). Although homosexual activity, intravenous drug use, and sex with a partner at risk were common risk factors for seropositive clients, after two interviews 17% of men and 38% of infected women did not report traditional risk factors for HIV infection. Most clients were asymptomatic or had generalized lymphadenopathy at the time of HIV diagnosis. Health care resources for these individuals were limited; 62% of men and 85% of women either had no health insurance or received public assistance. Routine, voluntary, confidential HIV counseling and testing is a practical, effective means to identify HIV-infected individuals among clients being treated at STD clinics. Identification of these individuals early in the course of infection provides opportunities to implement early follow-up and therapy, to counsel clients to help prevent further spread of infection, and to obtain useful information for projecting future health care needs and policy.