We found high completion rates for all seven instruments, with only a small number of items missing. Total scores for the instruments varied across patients, with the EQ-5D and PEI having a relatively high prevalence of maximum and minimum scores respectively, and most instruments being susceptible for change in the period between baseline and after four weeks. Some strong associations were found between the seven instruments, and between instruments and other measures such as treatment satisfaction and non-specific symptoms, but overall correlations tended to be weak or moderate. Based on our predefined criteria none of the seven instruments seem to stand out in a positive or negative way, and their potential use as PROMs should be studied more elaborately. Finally, the low response rate needs to be considered if PROMs are used in performance measurement systems, because this could lead to selection bias.
Our study is one of the first to explore the use of generic patient-reported outcome measures in primary care. In the US, the Patient-Reported Outcome Measurement Information Systems (PROMIS) aims at the continuing development of patient-reported measures that are comparable across studies and diseases . These measures focus on the domains physical-, mental- and social health, and in the current literature on PROMs we also see a focus on quality of life. The present study adds that it explores a broad set of outcome domains (i.e. empowerment, mental health, physical health, general health, enablement and perceived treatment outcome) that all seem to be of importance in primary care.
The present study had a low response compared to recent studies conducted in Dutch general practice [29, 30]. This low response may indicate selection bias, making it uncertain whether the sample reflected the general practice population. If such a measure were to be used as a performance measure, a low response would have its implications on interpreting the data. In our study we did not send a reminder, because we obtained patients’ contact information only after their return of the baseline questionnaire. One potential explanation for the low response rate is the length of the questionnaire. Shortening the measure might result in an increased response in future studies, as has been demonstrated in previous studies . The relatively small size of the study limited the possibility to detect small differences in time or between groups of patients, and significant associations between instruments and other measures. This makes it hard to draw firm conclusions from this study regarding the seven instruments, and replication in larger studies is required with a sample size of at least 400 patients. Despite these limitations, the study provided a number of important leads to the further development of PROMs for adoption in primary care.
Ideally, PROMs are measured before and after a specific intervention. In general practice, however, it is often difficult to determine a clear start and endpoint of treatment. In this study we had two measure moments, both after the consultation with the physician. Therefore the change may reflect effectiveness of interventions, natural course of symptoms, or measurement error. Because continuity of care is one of the hallmarks of general practice, interventions are not limited to one episode of care but cover patient’ health needs longitudinally [4, 32]. The data therefore could still express performance of general practice. Further research is needed to determine if other measure moments than those used in the present study are favourable in primary care.
The seven included instruments were frequently subject of study in previous research, though only limited as outcome measures in the setting of a generic population in general practice.
In our study we found a low responsiveness to change of the EQ-5D, also reflected by a high prevalence of maximum scores at both baseline and after four weeks. Previous studies showed ambiguous results regarding responsiveness of the EQ-5D [33, 34]. This might be explained by the different settings in which these studies took place. Our findings suggest that for a generic population visiting the GP other instruments that measure quality of life such as the SF-12 might be more appropriate, though no firm conclusions can be drawn.
The EC-17 specifically focuses on measuring main skills and behaviours needed to effectively manage ones chronic disease. Some of the items of the EC-17 are explicitly targeted at the patients’ disease. This resulted in a relatively low number of applicable answers on this instrument, since not all patients in our study population had a disease. The PAM-13 also focuses on chronic patients, though items are targeted at the patients’ health instead of the patients’ disease, which might explain why this instrument resulted in a higher response rate. This might opt for including the PAM-13 for measuring empowerment, though its validation for a general population in the primary care setting needs be studied.
Previous research that studied the outcome of patient consultations found associations between some of the used instruments and other measures, such as the PEI and the patients’ health status  and the PEI and treatment satisfaction , showed ambiguous results regarding the relation between health status and treatment satisfaction [26, 36], and related the presence of non-specific symptoms to emotional distress . In our study we only found a few strong associations, such as that between the GHQ and SF-12 MCS scores, which was to be expected since they both measure mental health, and between treatment satisfaction and the physical component scale of the SF-12. No other strong associations were found between instruments, or with other measures.
This study is to our knowledge one of the first that studies several previously validated questionnaires on different domains as potential PROMs in primary care. It may be used in the further exploration of adapting PROMs in general practice, though our findings are only preliminary results and further research is needed. We think that embedding a short informative measure in the care delivery process where it acts as a feedback tool on the patients’ level brings along opportunities. This way the added value for both GP and patient is clear, and it is easier for the GP to act upon this feedback in daily practice if needed. On the other side, embedding PROMs in the care process increases workload for the GP, which needs to be taken into consideration. The potential use of the used instruments as an individual feedback tool in the primary care setting should be studied more elaborately as well. Further research is needed to determine the psychometric properties of previously validated instruments in the current setting of study (i.e. generic primary health care population). Finally, the relation between the studied instruments with relevant clinical measures and the quality of delivered care is a point of interest for future studies.