Browsing by Subject "concordance"

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    Establishing the minimal sufficient number of measurements to validate a 24h blood pressure recording
    (2018-05-17) Agarwal, Rajiv; Tu, Wanzhu
    Background: Ambulatory blood pressure (BP) monitoring (ABPM) remains a reference standard but the number of readings required to make the measurement valid has not been empirically validated. Methods: Among 360 patients with chronic kidney disease and 38 healthy controls, BP was recorded 2 per hour during the night and 3 per hour during the day over 24h using a validated ABPM device; all had at least 90% of the expected readings. From this full set of ABPM recording, a variable number of BP measurements were selected and we compared the performance of the selected readings against that of the full sample using random or sequential selection schemes. To address the question whether random or sequential selection schemes affect the diagnostic performance in diagnosing hypertension control we compared the diagnostic decisions reached with the subsample and the full sample using area under the receiver operating-characteristic curves (AUC ROC). To answer the question regarding the number of readings needed to achieve over 90% coverage of the mean BP of the full ABPM sample we ascertained the point and confidence interval (CI) estimates based on the selected data. Results: To diagnose hypertension control, the number of readings randomly drawn to establish lower bound with 2.5% error of area under the receiver operating-characteristic curve (AUC ROC) of 0.9 was 3, 0.95 was 7, and 0.975 was 13 . In contrast, the corresponding number of readings with serial selections was 18, 30 and 39 respectively. With a random selection scheme, 18 readings provided 80% coverage of the 90th percentile of CI of the true systolic BP mean, for 90% coverage, 26 readings were needed, for 95% coverage 33. With serial selections, the number of readings increased to 42, 47, and 50 respectively. Similar results emerged for diastolic BP. Conclusions: For diagnosing hypertension control 3 random measurements or 18 serial measurements is sufficient. For quantitative analysis, the minimal sufficient number of 24h ambulatory BP is 26 random recordings or 42 serial recordings.
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    Genotype-specific Concordance of Chlamydia trachomatis Genital Infection within Heterosexual Partnerships
    (Lippincott, Williams & Wilkins, 2016-12) Schillinger, Julia A.; Katz, Barry P.; Markowitz, Lauri E.; Braslins, Phillip G.; Shrier, Lydia A.; Madico, Guillermo; Van Der Pol, Barbara; Orr, Donald P.; Rice, Peter A.; Batteiger, Byron E.; Biostatistics, School of Public Health
    Background Sexual transmission rates of Chlamydia trachomatis (Ct) cannot be measured directly; however, the study of concordance of Ct infection in sexual partnerships (dyads) can help to illuminate factors influencing Ct transmission. Methods Heterosexual men and women with Ct infection and their sex partners were enrolled and partner-specific coital and behavioral data collected for the prior 30 days. Microbiological data included Ct culture, nucleic acid amplification testing (NAAT), quantitative Ct polymerase chain reaction (qPCR), and ompA genotyping. We measured Ct concordance in dyads, and factors (correlates) associated with concordance. Results 121 women and 125 men formed 128 dyads. Overall, 72.9% of male partners of NAAT-positive women and 68.6% of female partners of NAAT-positive men were Ct-infected. Concordance was more common in dyads with culture-positive members (78.6% of male partners, 77% of female partners). Partners of women and men who were NAAT-positive only had lower concordance (33.3%, 46.4%, respectively). Women in concordant dyads had significantly higher median endocervical qPCR values (3,032) compared with CT-infected women in discordant dyads (1,013 IFU DNA equivalents per ml), p<0.01. Among 54 Ct-concordant dyads with ompA genotype data for both members, 96.2% had identical genotypes. Conclusions Higher organism load appears associated with concordance among women. Same-genotype chlamydial concordance was high in sexual partnerships. No behavioral factors were sufficiently discriminating to guide partner services activities. Findings may help model coitus-specific transmission probabilities.