Rademakers et al. BMC Public Health 2012, 12:577 http://www.biomedcentral.com/1471-2458/12/577 forward translation, expert panel meeting, backward translation, pre-testing/cognitive interviewing and con- sensus about the final version. Two independent Dutch translators performed the forward translation. The ex- pert panel included both translators and three research- ers with an expertise in chronic care, diversity in patient groups and measurement development. Discrepancies between the two translations were discussed and resolved. At the end of the expert meeting a single trans- lation of the PAM 13 was agreed upon. This instrument was then translated back into English. There were only a few minor textual discrepancies between the backward translation and the original instrument, which led to the conclusion that the Dutch translation was satisfactory and ready for pre-testing. Pre-testing was done in a focus group and 11 individ- ual cognitive interviews. A sample of 185 former partici- pants of the Dutch National Panel of people with Chronic illness or Disability (NPCD) were asked to par- ticipate in the pre-test. Five agreed to take part in the focus group (3 male, 2 female, mean age 64), whereas 11 preferred an interview (5 male, 6 female, mean age 65). Former participants were chosen because a sample from the current members of the Panel would be drawn for the main study (see under participants). In both the focus group and the interviews, respondents filled out the instrument at the beginning of the session. Then, the moderator (JR) or interviewer (JN) would ask questions about the general comprehensiveness of the instrument. Subsequently, each of the 13 items of the PAM was dis- cussed. Respondents were asked to think out loud, con- templating about their interpretation and the possible meaning and phrasing of the item. Also the answering categories were discussed. The focus group and cogni- tive interviews didn’t lead to major alterations in the Dutch translation of the PAM 13, though some items were slightly rephrased. The final version of the instrument (PAM 13-Dutch) is attached as an Additional file 1 to this paper (copyright Insignia Health www. InsigniaHealth.com). Participants The PAM 13-Dutch was sent to 2542 members of the Dutch National Panel of people with Chronic illness or Disability (NPCD) in April 2010 (study A) and again to 973 members in June 2010 (study B). The second sample were patients with Asthma and/or COPD, who had also received a questionnaire in study A. By doing so, the test-retest reliability of the instrument could be established. The Dutch National Panel of people with Chronic ill- ness or Disability (NPCD) is a nationwide prospective panel-study in the Netherlands. NPCD consists of over 4000 people aged 15 years and over with medically Page 3 of 7 diagnosed chronic disease(s) and/or moderate to severe levels of physical disability. It has been set up to provide information with respect to the consequences of chronic illness and disability from the patient’s perspective. For the purpose of this study, we only selected panel mem- bers who had been diagnosed with a somatic chronic disease. Patients are included in the panel on the basis of a the oldest medical diagnosis of a chronic disease (=index disease). The medical diagnosis or diagnoses of chronic diseases of the patients were registered by their general practitioner (GP) using the International Classi- fication of Primary Care (ICPC). The registered chronic disease (oldest diagnosis = index disease) of the partici- pants in study A could be classified into nine broad cat- egories: asthma and COPD (together 38%), diabetes (12%), cardiovascular diseases (11%), rheumatic diseases (11%), neurological diseases (6%), cancer (4%), chronic digestive diseases (4%) en other chronic diseases (15%). Asthma and COPD patients were oversampled in study A because they would be approached again for study B. We had chosen to validate the PAM 13-Dutch in the NPCD subsample of people with a chronic illness be- cause it closely resembled the samples which were used in the validation studies in the United States and Denmark [2,14]. In the USA, a group of 1515 randomly selected adults (age 45+) participated in the development study, of which 79% had at least one chronic disease [2]. In the Danish study, 467 patients (age 43 - 75 years) who were diagnosed with different aspects of dysglycaemia (Impaired Fasting Glucose, Impaired Glucose Tolerance and Type 2 diabetes) participated [14]. In both data collections, the instrument was part of a larger survey on chronic care and self-management. When entering the Panel, the participants give informed consent to the use of their data for research purposes. According to Dutch law, no further ethical approval is required. Measures Age, gender, education level and self-reported health were measured as background variables. Education in the Netherlands was divided in three groups; low (no, primary school, or vocational training), middle (second- ary or vocational education) or high (professional higher education or university). Self-reported health is the first item of the SF 36 (http://www.sf-36.org). Patient activation was measured using the PAM 13- Dutch, which consists of 13 items. The answering cat- egories per item are 4-point Likert scales, ranging from totally disagree to totally agree and ‘non applicable’. The design of the instrument reflects the four stages of acti- vation in a progressing difficulty of the items: level 1 (patients believe that their role is important; items 1 and 2), level 2 (patients have confidence and knowledge to