Human papillomavirus as a form of risk assessment.

There is a huge amount of interest in the use of human papillomavirus testing to improve both the sensitivity and specificity of cervical screening. Although oncogenic human papillomavirus subtypes are recognized to be the most important factor in the development of cervical disease, only a minority of such infections results in invasive cancer. Given our current, albeit limited, knowledge of the natural history of human papillomavirus infection and the development of cervical intra-epithelial neoplasia, it may be possible to identify well-defined high-risk groups of women. Such groups may benefit from intensive surveillance, or indeed new developments in immunoprophylaxis, while allowing low-risk women less screening intervention. Known high-risk groups include those with chronic immunosuppression and previous treatment for high-grade cervical intra-epithelial neoplasia. Lowering the upper age limit for cervical screening is already under consideration because of the low incidence of both human papillomavirus infection and cervical intra-epithelial neoplasia in older women, and human papillomavirus testing could rationalize the screening programme.

Socioeconomic predictors of high allergen levels in homes in the greater Boston area.

In the United States, childhood asthma morbidity and prevalence rates are the highest in less affluent urban minority communities. More than 80% of childhood asthmatics are allergic to one or more inhalant allergens. We evaluated whether socioeconomic status was associated with a differential in the levels and types of indoor home allergens. Dust samples for an ELISA allergen assay were collected from the homes of 499 families as part of a metropolitan Boston, Massachusetts, longitudinal birth cohort study of home allergens and asthma in children with a parental history of asthma or allergy. The proportion of homes with maximum home allergen levels in the highest category was 42% for dust mite allergen (> or = 10 microg/g Der p 1 or Der f 1), 13% for cockroach allergen (> or = 2 U/g Bla g 1 or Bla g 2), 26% for cat allergen (> or = 8 microg/g Fel d 1), and 20% for dog allergen (> or = 10 microg/g Can f 1). Homes in the high-poverty area (> 20% of the population below the poverty level) were more likely to have high cockroach allergen levels than homes in the low-poverty area [51 vs. 3%; OR, 33; 95% confidence interval (CI), 12-90], but less likely to have high levels of dust mite allergen (16 vs. 53%; OR, 0.2; CI, 0.1-0.4). Lower family income, less maternal education, and race/ethnicity (black or Hispanic vs. white) were also associated with a lower risk of high dust mite levels and a greater risk of high cockroach allergen levels. Within a single U.S. metropolitan area we found marked between-community differences in the types of allergens present in the home, but not necessarily in the overall burden of allergen exposure.

The effect of serial dilution error on calibration inference in immunoassay.

A common practice in immunoassay is the use of sequential dilutions of an initial stock solution of the antigen of interest to obtain standard samples in a desired concentration range. Nonlinear, heteroscedastic regression models are a common framework for analysis, and the usual methods for fitting the model assume that measured responses on the standards are independent. However, the dilution procedure introduces a propagation of random measurement error that may invalidate this assumption. We demonstrate that failure to account for serial dilution error in calibration inference on unknown samples leads to serious inaccuracy of assessments of assay precision such as confidence intervals and precision profiles. Techniques for taking serial dilution error into account based on data from multiple assay runs are discussed and are shown to yield valid calibration inferences.