Confidence intervals for biomarker-based human immunodeficiency virus incidence estimates and differences using prevalent data

Prevalent biologic specimens can be used to estimate human immunodeficiency virus (HIV) incidence using a two-stage immunologic testing algorithm that hinges on the average time, T, between testing HIV-positive on highly sensitive enzyme immunoassays and testing HIV-positive on less sensitive enzyme immunoassays. Common approaches to confidence interval (CI) estimation for this incidence measure have included 1) ignoring the random error in T or 2) employing a Bonferroni adjustment of the box method. The authors present alternative Monte Carlo-based CIs for this incidence measure, as well as CIs for the biomarker-based incidence difference; standard approaches to CIs are typically appropriate for the incidence ratio. Using American Red Cross blood donor data as an example, the authors found that ignoring the random error in T provides a 95% CI for incidence as much as 0.26 times the width of the Monte Carlo CI, while the Bonferroni-box method provides a 95% CI as much as 1.57 times the width of the Monte Carlo CI. Further research is needed to understand under what circumstances the proposed Monte Carlo methods fail to provide valid CIs. The Monte Carlo-based CI may be preferable to competing methods because of the ease of extension to the incidence difference or to exploration of departures from assumptions.

The antihypertensive effects of the Jamaican Cho-Cho (Sechium edule)

The experiments reported in this study constitute a preliminary investigation into the possible hypotensive effect of the Jamaican Cho-Cho (Sechium edule). Experiments were conducted in a random and blind fashion on two sub species of Sechium edule. Both the pulp and the peel were examined for hypotensive activity. Water-soluble extracts were prepared from these components of the fruit and injected into anaesthetised rats. Various cardiovascular parameters were measured including heart rate, mean arterial pressure (MAP) and several ECG intervals. We report that all extracts tested produced a fall in blood pressure with little change in ECG intervals. Extract B produced the least change in heart rate with a fall in MAP of approximately 23 mmHg. Changes in heart rate with all extracts appeared to be minimal as an ED25 value could only be determined for extract A, and ED10 values could not be evaluated for extracts C and D. The mechanism(s) by which these extracts produce their hypotensive effects could not be determined in these preliminary experiments. However, it appears not to involve direct effects on cardiac tissue. This conclusion is based on the finding that it took a minimum of 10 to 15 seconds for the hypotensive action to manifest post bolus. Future experiments will be aimed at delineating the mechanism(s) involved in decreasing MAP.(Au)

Sexually transmitted diseases are common in women attending Jamaican family planning clinics and appropriate detection tools are lacking

OBJECTIVES: To assess sexually transmitted diseases (STD) among women attending Jamaican family planning clinics and to evaluate decision models as alternatives to STD laboratory diagnosis. METHODS: Women attending two family planning clinics in Kingston were interviewed and tested for syphilis seroreactivity using toluidine red unheated serum test and Treponema pallidum haemagglutination, for gonorrhoea using culture, for chalamydial infection using enzyme linked immunoassay, and for trichomoniasis using culture. Urine was tested with leucocyte esterase dipstick (LED). The women were treated based upon a clinical algorithm. Computer simulations explored the use of risk inclusive decision models for detection of cervical infection and/or trichomoniasis. RESULTS: Among 767 women, 206 (26.9 percent) had at least one STD. The prevalence of gonorrhoea was 2.7 percent: chlamydial infection 12.2 percent, gonococcal and/or chlamydial cervical infection 14.1 percent; trichomoniasis 11.5 percent; syphilis seroreactivity 5.9 percent. The clinical algorithm was 3.7 percent sensitive and 96.7 percent specific in detecting cervical infection. Detection of cervical infection and/or trichomoniasis was 63.5 percent sensitive and 60.6 percent specific using LE and 57.7 percent sensitive and 46.2 percent specific using the risk inclusive algorithm employed in Jamaica STD clinics. Either cervical friability or LED (+) or family planning clinic attender less than 25 years old with more than one sexual partner in the past year was 72.5 percent sensitive and 53.3 percent specific. The positive predictive values of the STD clinic algorithm, LED, and two developed decision models ranged from 25.0 percent to 33.4 percent to detect cervical infection and/or trichomoniasis in these women. CONCLUSION: STDs were quite prevalent in these mainly asymptomatic family planning clinic attenders. None of the evaluated decision models can be considered a good alternative to case detection using laboratory diagnosis. Appropriate detection tools are needed. In the meantime, available STD control strategies should be maximised, such as promotion of condom use; adequate treatment of symptomatic STD patients and partners; and education of women and men (AU)