Increasing response rates from physicians in oncology research: a structured literature review and data from a recent physician survey.

Although the physician survey has become an important tool for oncology-focused health services research, such surveys often achieve low response rates. This mini-review reports the results of a structured review of the literature relating to increasing response rates for physician surveys, as well as our own experience from a survey of physicians as to their referral practices for suspected haematologic malignancy in the United States. PubMed and PsychINFO databases were used to identify methodological articles assessing factors that influence response rates for physician surveys; the results were tabulated and reviewed for trends. We also analysed the impact of a follow-up telephone call by a physician investigator to initial non-responders in our own mailed physician survey, comparing the characteristics of those who responded before vs after the call. The systematic review suggested that monetary incentives and paper (vs web or email) surveys increase response rates. In our own survey, follow-up telephone calls increased the response rate from 43.7% to 70.5%, with little discernible difference in the characteristics of early vs later responders. We conclude that in addition to monetary incentives and paper surveys, physician-to-physician follow-up telephone calls are an effective method to increase response rates in oncology-focused physician surveys.

Hepatocyte inducible nitric oxide synthesis is influenced in vitro by cell density.

Hepatocyte plating density is known to affect cell function. Human and rat hepatocytes have been shown to express the inducible nitric oxide synthase (INOS) in response to cytokines plus lipopolysaccharide (LPS). The following studies were performed to determine the effects of hepatocyte plating density on the regulation of INOS. Rat hepatocytes were plated at densities from 10(4) to 20 x 10(4) hepatocytes/cm2 and stimulated with a combination of LPS, interferon-gamma, interleukin-1, and tumor necrosis factor. We found that NO2- plus NO3- released from stimulated hepatocytes declines with increasing hepatocyte density. Similar effects were seen for 3',5'-cyclic monophosphate release into supernatants and in the amount of nonheme iron-nitrosyl signals measured by electron paramagnetic resonance spectroscopy. Limitations of substrate (L-arginine) and 5,6,7,8-tetrahydrobiopterin were excluded as cause of the reduced nitric oxide generation at higher densities. Although mRNA levels for INOS were not influenced when measured at 24 h, there was a marked reduction in INOS enzyme activity and INOS protein detectable by Western blotting at higher cell density. Total protein synthesis decreased as hepatocyte density increased in both nonstimulated and stimulated hepatocytes at higher cell densities. These data suggest that reduced INOS translation may account for the density-dependent reduction in INOS activity in cultured hepatocytes. The importance of this phenomenon remains to be determined in vivo but has important implications for the in vitro study of INOS expression.