Last data update: May 13, 2024. (Total: 46773 publications since 2009)
Records 1-3 (of 3 Records) |
Query Trace: Karon JM[original query] |
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Comparison of models for analyzing two-group, cross-sectional data with a Gaussian outcome subject to a detection limit
Wiegand RE , Rose CE , Karon JM . Stat Methods Med Res 2014 25 (6) 2733-2749 A potential difficulty in the analysis of biomarker data occurs when data are subject to a detection limit. This detection limit is often defined as the point at which the true values cannot be measured reliably. Multiple, regression-type models designed to analyze such data exist. Studies have compared the bias among such models, but few have compared their statistical power. This simulation study provides a comparison of approaches for analyzing two-group, cross-sectional data with a Gaussian-distributed outcome by exploring statistical power and effect size confidence interval coverage of four models able to be implemented in standard software. We found using a Tobit model fit by maximum likelihood provides the best power and coverage. An example using human immunodeficiency virus type 1 ribonucleic acid data is used to illustrate the inferential differences in these models. |
High-risk human papillomavirus reactivation in human immunodeficiency virus-infected women: risk factors for cervical viral shedding
Theiler RN , Farr SL , Karon JM , Paramsothy P , Viscidi R , Duerr A , Cu-Uvin S , Sobel J , Shah K , Klein RS , Jamieson DJ . Obstet Gynecol 2010 115 (6) 1150-1158 OBJECTIVE: To evaluate the presence of and estimate risk factors for reactivation of latent high-risk human papillomavirus (HPV) cervical infection in human immunodeficiency virus (HIV)-infected and HIV-uninfected women. METHODS: Data from 898 women in the HIV Epidemiology Research Study (HERS) were used to evaluate cervical HPV latency and reactivation. Prior exposure to HPV types (16, 18, 31, 35, and 45) was determined by serologic testing at enrollment, and cervical shedding of HPV was detected by polymerase chain reaction at 6-month intervals. Human papillomavirus cervical shedding and sexual history were used to estimate rates of reactivation and recurrence. Repeated measures survival analysis was used to estimate hazard ratios and 95% confidence intervals for reactivation and recurrence. Rates of total HPV shedding (recurrence and reactivation) during follow-up were assessed by HIV status and rate ratios were calculated. RESULTS: Reactivation of latent HPV infections was observed in HIV-infected women, but few reactivation events were identified in HIV-uninfected women. Factors consistently associated with reactivation in HIV-infected women included CD4 count less than 200/mm and age younger than 35 years. Women infected with HIV had 1.8 to 8.2 times higher rates of viral shedding (reactivation plus recurrence) compared with HIV-uninfected women. CONCLUSION: Women with a history of cervical HPV infection may be at risk of reactivation of latent viral infection even in the absence of sexual activity, and this risk is higher in women with HIV infection. LEVEL OF EVIDENCE: II. |
HIV genital shedding and safety of Carraguard use by HIV-infected women: a crossover trial in Thailand
McLean CA , van de Wijgert JH , Jones HE , Karon JM , McNicoll JM , Whitehead SJ , Braunstein S , Achalapong J , Chaikummao S , Tappero JW , Markowitz LE , Kilmarx PH . AIDS 2010 24 (5) 717-22 OBJECTIVE: To evaluate the safety, including impact on genital HIV RNA shedding, of Carraguard vaginal gel in HIV-infected women. DESIGN: This is a randomized, controlled, crossover study of Carraguard in HIV-infected women in Thailand. METHODS: Each woman (CD4 cell count 51-500 cells/mul and not on antiretroviral therapy) used each treatment (Carraguard, methylcellulose placebo, and no-product) once daily for 7 days during each 1-month period (3-week wash-out). Women were randomized to one of the six possible treatment sequences. Safety assessments were conducted at baseline (pregel), 15 min postgel, day 7, and day 14, and included HIV RNA measurements in cervicovaginal lavage (CVL) specimens. RESULTS: Sixty women were enrolled, and 99% of scheduled study visits were completed. At baseline, median age (34 years), CD4 lymphocyte count (296 cells/mul), plasma HIV viral load (4.6 log10 copies/ml), CVL HIV viral load (3.1 log10 total copies per CVL), and sexual behaviors were similar among randomization groups. HIV viral load, leukocyte and hemoglobin levels, and epithelial cell counts in CVLs were lower 15 min after application of Carraguard or placebo compared with no product; CVL HIV viral load was still lower at day 7 but returned to baseline by day 14. Carraguard use was not associated with prevalent or incident genital findings or abnormal vaginal flora. CONCLUSION: Carraguard appears to be well tolerated for once-daily vaginal use by HIV-infected women. The observed reduction in CVL HIV viral load in the gel months may be clinically relevant but could have resulted from interference with sample collection by study gels. |
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