[Validity of patient self report data in rehabilitation research: identifying circumstances of the patients' completion of questionnaires].
BACKGROUND
Self-report questionnaires have become wide-spread and are an integral part in different fields of rehabilitation. However, it is still unclear to what extent the validity of the patients' reports is affected by motivational factors. How difficult is it for the patient to fill out questionnaires? What are the situational characteristics in which the patients fill them out? The present study aims to identify the situational, motivational and cognitive requisites of the respondents and to analyse possible impacts on the validity of self-reports.


METHODS
A total of n = 105 patients scheduled for inpatient rehabilitation were interviewed by means of a guided open-ended interview in the admission phase. It is a consecutive sample of all admissions in two rehabilitation clinics in Schleswig-Holstein, which provide each patient with a questionnaire to fill out prior to their stay. The analysis involved a description of statements (categories) that have been derived by content analysis based on the patient interviews. In addition, physicians rated various patients' characteristics at the end of their hospital stay.


RESULTS
The participation rate of the patients was 95.5 %. Of all patients, 95 % filled out the questionnaires at home, 69 % without a break. 57 % of the patients interviewed had filled out the questionnaires by themselves without any help, another 22 % worked it through together with their partner or spouse. The extent of influence on the responses appeared to be dependent on the amount of help necessary. In a substantial number of patients the questionnaires were regarded as an "official" document that had to be worked through meticulously. Physicians attested 96 % of the patients to have provided honest reports with regard to personal characteristics, and 95 % to have shown a sufficient degree of willingness of self-disclosure. By and large the patients' perceptions of themselves fit with the perceptions the physician in 76 % of the patients from the physicians' point of view. All patients except one were attested a positive motivation to take part in rehabilitation activities in the clinic by the physician. In individual cases there were substantial deficits of cognitive capacities necessary to work through a questionnaire, as well as limitations in literacy. Four patients had insufficient mastery of the German language.


CONCLUSIONS
The vast majority of the patients possessed sufficient motivational and cognitive prerequisites to provide valid self-reports. Patients with problems in responding asked partners or others for help, its impact on the self-reports being as yet not clear-cut. In individual cases it can not be ruled out that patients who think about early retirement provide distorted statements.
Institut für Sozialmedizin, Universitätsklinikum Schleswig-Holstein, Campus Lübeck. thorsten.meyer@sozmed.uni-luebeck.de
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D000328:Adult; D000368:Aged; D001291:Attitude of Health Personnel; D004522:Educational Status; D005260:Female; D006801:Humans; D007406:Interview, Psychological; D008297:Male; D008875:Middle Aged; D009042:Motivation; D010343:Patient Admission; D010349:Patient Compliance / Q000523:psychology*; D012046:Rehabilitation / Q000523:psychology*; D012047:Rehabilitation Centers; D015203:Reproducibility of Results; D012106:Research; D012650:Self Disclosure; D020377:Self Efficacy; D012718:Set, Psychology; D012803:Sick Role; D011795:Surveys and Questionnaires / Q000592:standards; D014342:Truth Disclosure