Preference-based health outcome measures in low back pain

Preference-based health outcome measures were considered in two settings. In the clinical context, utility assessment using the VAS, TTO or SG was described. It is recognized that formal utility assessment is generally not needed in day-to-day clinical practice. When the need to explicitly value alternative health outcomes arises, the VAS is recommended because of its ease of implementation. In the health policy context, preference classification systems are recommended for valuing health when a cost-effectiveness analysis of alternative health care interventions is planned. At present, there is little evidence to base choice of one system over another for assessing the cost-effectiveness of low back pain interventions.     

Lung bullae and pulmonary fibrosis associated with marijuana smoking

A 26‐year‐old man with a history of heavy marijuana and minimal tobacco use was found to have extensive bilateral lung bullae and interstitial fibrosis, heavily infiltrated by pigmented macrophages. These features can be associated with marijuana smoking. The differential diagnoses in this patient are also discussed.     

Using instrumental variables to estimate a Cox’s proportional hazards regression subject to additive confounding

The estimation of treatment effects is one of the primary goals of statistics in medicine. Estimation based on observational studies is subject to confounding. Statistical methods for controlling bias due to confounding include regression adjustment, propensity scores and inverse probability weighted estimators. These methods require that all confounders are recorded in the data. The method of instrumental variables (IVs) can eliminate bias in observational studies even in the absence of information on confounders. We propose a method for integrating IVs within the framework of Cox’s proportional hazards model and demonstrate the conditions under which it recovers the causal effect of treatment. The methodology is based on the approximate orthogonality of an instrument with unobserved confounders among those at risk. We derive an estimator as the solution to an estimating equation that resembles the score equation of the partial likelihood in much the same way as the traditional IV estimator resembles the normal equations. To justify this IV estimator for a Cox model we perform simulations to evaluate its operating characteristics. Finally, we apply the estimator to an observational study of the effect of coronary catheterization on survival.     

Examination of the Construct Validity of Impact™ Computerized Test,Traditional, and Experimental Neuropsychological Measures

Although computerized neuropsychological screening is becoming a standard for sports concussion identification and management, convergent validity studies are limited. Such studies are important for several reasons: reference to established measures is needed to establish validity; examination of the computerized battery relative to a more traditional comprehensive battery will help understand the strengths and limitations of the computer battery; and such an examination will help inform the output of the computerized battery. We compared scores on the ImPACT? battery to a comprehensive battery of traditional neuropsychological measures and several experimental measures used in the assessment of sports-related concussion in 54 healthy male athletes. Convergent validity was demonstrated for four of the five ImPACT? domain scores. Two cognitive domains often compromised as a result of mild TBI were not directly identified by the ImPACT? battery: sustained attention and auditory working memory. Affective symptoms correlated with performance on measures of attention and working memory. In this healthy sample the correlations between the domains covered by ImPACT? and the neuropsychological battery supports ImPACT? as a useful screening tool for assessing many of the cognitive factors related to mTBI. However, the data suggest other sources of data need to be considered when identifying and managing concussions.