Patients. We approached patients who were older than 18 years and had 1 or more recurring problems who presented to their physician’s office. Patients were excluded if they were too ill or disabled to answer questions, had no presenting problem, were in the office for counseling, were accompanied by another person, were not fluent in English, were hard of hearing, or were cognitively impaired. They were approached before they saw the physician and were blind to the study hypotheses.
Sample Size Estimation. The sample size required for correlations of 0.20 to be detected with an a set at 0.05 (2 tailed) and a b set at 0.10 was 25915 patients. Further inflation by 10% to account for the effect of clustering on multiple regression16 was thought to be reasonable (259÷0.9=288). Expecting 75% to cooperate, we aimed to approach 384 patients (288÷0.75).
Measure of Patient-Centered Communication Score. The patient-centered communication score is based on 3 of the 6 components of the model of patient-centered medicine.17-20 The first component (exploring the disease and the illness experience) received a high score when the physician explored the patients’ symptoms, prompts, feelings, ideas, function, and expectations. The second component (understanding the whole person) received a high score when the physician elicited and explored issues relating to life cycle, personality, or life context, including family. The third component (finding common ground) received a high score when the physician clearly described the problem and the management plan, answered questions about them, and discussed and agreed on them with the patient. Scoring sheets and procedures are described in detail elsewhere.21 Scores could range from 0 (not at all patient centered) to 100 (very patient centered).
Interrater reliability has been established in earlier versions of the measure and for the current version (r=0.69, 0.84, and 0.80 among 3 raters,22 0.91 among 2 raters,23 and 0.83 for n=19 for our study). Intrarater reliability was 0.73 (n=20).
Correlations with global scores encompassing the 3 components supported the validity of the score (0.63 in an earlier study23 and 0.85 for our study, n=46).
Patient Perception of Patient-Centeredness. Based on the patient-centered model, a series of 14 items developed and validated in previous studies24,25 were used to assess the patients’ postencounter perceptions of how patient centered the interaction with the physician had been.† Items were averaged into: total score, a subscore on exploring the disease and illness experience, and finding common ground. Low scores represented patient centeredness.
Patient Recovery from Discomfort and Concerns. The primary health outcome was the recovery measure based on the patients’ self-administered report on visual analogue scales (VAS) of the severity of the symptom they identified as the main presenting problem and their concern about that problem at 2 points: the postencounter interview and the follow-up 2 months later.26,27 VAS have been tested for reliability and validity in studies of pain and nausea (correlation of 0.75 with an intensity score).26 Each of the symptom recovery variables was continuous.
Patient Health Status. The Medical Outcomes Study Short Form-36 (SF-36) was used to assess self-reported secondary health outcomes. This valid and reliable measure18 is a multidimensional assessment of: physical health, mental health, perception of health, social health, pain, and role function. All were continuous variables except role function, for which the distribution of scores necessitated dichotomizing.
Medical Care. The care provided during the 2 months following the audiotaped encounter was assessed by chart review (adapted from Bass and coworkers24) by 3 medical doctors (I.R.M., J.O., J.J.) blind to the identity of the family physician and the patient, and also to the patient-centered scores. Items abstracted were: the total number of visits during the 2 months (continuous variable); the number and kind of diagnostic tests ordered during the 2 months that were relevant to the problems presented at the audiotaped visit (dichotomous); and the number and kinds of referrals made during the 2 months that were relevant to the problems presented at the audiotaped visit (dichotomous).
Analysis. The hypotheses were tested using multiple regression for continuous outcomes and multiple logistic regression for dichotomous outcomes,29 both adjusted for the effect of the clustering of patients by physician using “procedure mixed” in SAS for continuous outcomes and using both “procedure logistic” and “procedure IML” in SAS for dichotomous outcomes.30 The unit of analysis was the patient.
The following confounding variables were included in preliminary multivariable analyses on the basis of their univariable relationships with outcomes at the level of P <.10: age, sex, number of family members at home, desire to share feelings, who initiated the visit, tense personality, coping skills, concomitant health problems, social support, marital status (married vs other), concomitant life problems, number of visits to the physician in the previous 12 months, and main problem (1 of 5 groups: digestive, musculoskeletal, respiratory, skin, and other).