tween day-to-day fluctuations in sputum viscosity and changes in the results of pulmonary function tests during the period of study. Discussion In the 5 patients studied, sputum viscosity was strongly negatively correlated with pulmonary function. Because patients producing the most viscous sputum also produced the most purulent specimens, the presence of infection may have influenced the results. However, as Cases 1, 4, and 5 produced the same number of purulent specimens, and significant differences have been shown between the viscosities of sputum samples from different patients regardless of purulence (Feather and Russell, 1970b), it seems likely that purulence is not the only factor involved.It is of interest to note that all of the 5 patients studied showed, at some time, evidence of reversible airways obstruction, which some workers have found to be absent (Cook et al., 1959; Beier et al., 1966). Our patients were selected in that they were all able to produce sputum, and this could be related to Mearns's (1968) suggestion that reversible airways obstruction might be indicative of insidious infection. This author noted response to isoprenaline to be most frequent in the group with a FVC of 60-79% ofthat predicted; theFVC of our patients ranged from 36-92% of the predicted values.The relation between sputum viscosity and dynamic lung volumes could have arisen either because patients with the highest sputum viscosity eventually develop the most severe pulmonary lesions, or because sputum viscosity increases as the severity of the respiratory disease progresses. Though no correlation could be shown between day-to-day changes in respiratory function and changes in sputum viscosity in individual patients over a fourweek period, it would be of interest to study more patients over a longer period of time. Summary A significant negative correlation between dynamic lung volumes and sputum viscosity has been shown in five patients with cystic fibrosis.

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Healthcare overuse is the provision of care in which the benefits do not justify the harms and/or costs. Overuse literature is poorly categorized thus impeding research, practice, and policy to reduce overuse and improve healthcare quality. We developed an overuse taxonomy and searched for and reviewed the healthcare overuse literature in an attempt to better understand and categorize research on overuse practice and patterns. We found that more than two-thirds of articles were observational (70%), the most prevalent purpose of overuse was treatment/secondary prevention (69%), the most common type of overuse was overtreatment (73%), drivers of and methods to reduce overuse were each discussed in about 40% of abstracts, and the most frequently mentioned clinical area was pharmacy. A high volume of overuse literature exists. However, the majority of overuse research is observational, descriptive, and focuses on overtreatment and overprescribing rather than methods to reduce overuse. Some overuse is not labelled as such. Our taxonomy adequately organized the existing literature and identified areas where additional research efforts are most needed. A common taxonomy, such as ours, could help researchers categorize their work, assist clinicians and policymakers in identifying and implementing findings, and guide future research to improve healthcare quality.

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