Participants and setting
From November 2011 until January 2012, every in-hospital patient above 16 years of age who was discharged from the University Hospital in Basel, Switzerland, had the opportunity to participate in this healthcare survey. Patients received a letter with both questionnaires and were requested to accept the redundancy of five questions on two different response scales and to answer all questions. If the discharged patients did not return the questionnaire, no reminders were sent out. The questionnaire was sent out in the following five languages: German, French, Italian, English and Turkish. If a patient had a different native language, they received the German version of the questionnaire.
The following socio-demographic variables were assessed for all patients: Age, gender, nationality, native language, emergency versus elective hospital admission, length of hospital stay, individual department where patients received their main treatment and hospital readmissions within the same study period. Since our anonymisation procedure was irreversible, re-admission information was limited to all in-hospital patients during the study period and was not available for the subpopulation of patients returning the complete questionnaire.
The anonymisation procedure of this quality control survey was approved by the local data protection committee (“Datenschutzbeauftragter des Kantons Basel-Stadt”, reference number 10_0147). Since the primary purpose of the survey was the quality control of in-hospital patients at the University Hospital Basel, the local ethics committee (“Ethikkommission beider Basel”) exempted the survey from formal ethical committee approval. Moreover, confidentiality was preserved by separating the data analysis team from the healthcare providers.
Questionnaires
1) Questionnaire using a numeric answering scale (NS)
In 2011, the Swiss National Association for Quality Development in Hospitals and Clinics (ANQ, http://www.anq.ch) has developed a questionnaire with the aim that every member of this association uses the questionnaire during one defined month of the year, leading to a yearly national quality evaluation of all hospitals in Switzerland. In order to obtain a larger sample, we have extended the survey to three months.
The five questions (Figure 1) covered four important domains, which indirectly rate patient satisfaction on an evaluation scale. The questions were ordered as follows: 1) behavioural intent to return to the hospital (one question), 2) quality of treatment (one question), 3) quality of medical information (two questions), and 4) question concerning judgement whether the patient was treated with respect and dignity (one question). The response scale is displayed on an 11-point numeric scale (NS) with anchors at both ends, presenting the negative answers first.
2) Questionnaire using a labelled answering scale (LS)
The questionnaire consists of 17 items (Figure 1 and webappendix: Additional file 1), whereby for the present study only the five questions, which are shared with the national survey, were considered. The questionnaire started with questions about the quality of information, followed by the question about respect and dignity, the quality of treatment and ended with the question about the intent to return. This questionnaire is based on the Picker questionnaire, which is a widely used and validated instrument for quality evaluation in hospital contexts [12]. The response scale is displayed on an adjectival scale with, according to the question, three or four labelled response categories, presenting the positive answers first. The labels included the following answering options: 1) Yes, of course; yes, I think so; no, I do not think so; of course not and 2) excellent; good; fair and poor; and 3) with three response categories yes, always; yes, sometimes; no.
Statistical analyses
Statistical analyses were conducted using Intercooled Stata Version 11.2 for Macintosh (StataCorp, College Station, TX, USA). Graphs were performed in Intercooled Stata Version 11.2 for Macintosh and in R system, version 2.14.2 (R Foundation for Statistical Computing. Vienna, Austria). We report 95% confidence intervals (CI), rather than p-values, in order to emphasise clinical relevance over statistical significance, because in this large data set, irrelevant differences are also statistically significant. According to the current guidelines for reporting observational data (STROBE) [13], we avoided significance tests for the evaluation of differences in baseline characteristics.
Baseline characteristics were summarised for all patients, questionnaire responders, non-responders and responders with no missing items. The latter group corresponds to the patients included in this analysis.
The answers on both response scales were summarised in a frequency table for comparison of the ceiling effect. The Cronbach’s alpha for the five questions on each response scale was calculated as a measure for internal consistency. Since the five items are all measuring patient satisfaction (i.e. are congeneric), the alpha is an estimate of the lower end of reliability [14]. Therefore, only the lower one-sided 95% confidence interval was computed to see whether it is significantly greater than some minimal value [15, 16]. Furthermore, the data were investigated using graphical displays (histogram, scatterplot) and the Spearman’s rank correlation coefficient with its 95% confidence intervals (CI) [17] to determine the amount of correlation between both response scales (NS and LS) for each item.
We calculated an overall percentage score for each of the two questionnaires’ results as a summary measure with a common metric. In the numeric scale questionnaire, we calculated the sum of the five answers, ranging from 5 to 55. In the adjectival scale questionnaire, we attributed values from 1 to 4 or 1 to 3, respectively, to the answer categories, resulting in a range from 5 to 17. Here, we assumed equal distance between the categories. The percentage score was calculated by dividing the sum of the answers by the maximum possible sum. For the calculation of the Spearman’s correlation coefficient and the overall percentage score, those patients who did not have any questions in the third and fourth questions were disregarded.
These analyses were repeated in an explorative way in the following prespecified subgroups: Elective versus emergency patients and short versus long hospitalisation, as defined by median split. We have chosen these subgroups since it is known from the literature that hospital length of stay and type of admission have an impact on satisfaction with hospital care [18, 19].