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Opportunities and limitations of general practice databases in pain research
Pain 137 (2008) 469–470 www.elsevier.com/locate/pain
Editorial
Opportunities and limitations of general practice databases in pain research
Dieleman et al.’s [2] investigation of neuropathic pain may trouble clinical pain specialists. It rides a little roughly over a clinician’s detailed approach to diagnosis and classification. The authors have based their research on one of an increasing number of databases drawn from primary care consultations. These are based on the routine recording and coding of illness and morbidity by family doctors or general practitioners (GPs) who do not necessarily use standard diagnostic labels for neuropathic pain syndromes in their daily practice. As with all forms of research data, such databases can be misused or misapplied. If their weaknesses are acknowledged and discussed, however, they have much to contribute to pain research. Dieleman’s paper provides an excellent example of how to use them carefully and creatively. Here we discuss some general issues. Measuring morbidity occurrence. In countries such as the UK and the Netherlands, general practices have a list of people from the general population registered for provision of primary care and access to secondary care. In such practices, morbidities are often routinely coded and recorded during consultations. Occurrence rates of morbidities can be calculated by relating the number of people consulting for a problem to the size and characteristics of the registered populations [4,8]. Hence GP databases are a source of routine statistics about morbidity occurrence. Such figures, however, will under-represent true occurrence in the population if not all cases are brought to the attention of a GP. This is a problem in health care systems with direct patient access to specialists, but even in countries with ‘‘gatekeeper” systems only a proportion of sufferers from common syndromes such as back pain will take them to their family doctor. So occurrence will relate to ‘‘pain for which consultation with the GP has been sought”. This matters less for conditions always seen by the GP, or when the objective is to measure health care use or to estimate associations with characteristics such as age and gender.
Labelling. Databases reflect what GPs choose to call things in usual clinical practice, and they do not usually incorporate standardised criteria for applying diagnostic labels. GPs work with uncertainty and early presentations; they watch for serious disease whilst accepting that symptoms are often undifferentiated when first presented. Many systems for coding morbidities, such as the International Classification of Primary Care, allow symptoms as well as definite diagnoses to be recorded. This is a big gain for epidemiology – better to have the big pool recorded (all labels relating to back pain, for example) than selected diagnoses made on spurious grounds. When there is a specific disease underlying presenting symptoms, this is likely to appear eventually in the GP record. Validation of database diagnoses for some ‘‘serious” diseases have been published. Dieleman provides one example of this; others have validated GP records against sources such as specialist records or assessments (e.g. [7]). Provided there is some validity and consistency when labels like carpal tunnel syndrome or trigeminal neuralgia are used, these datasets can be used for large-scale epidemiology research even if precision is lacking in individual patients. More difficult are diagnoses such as asthma or tenosynovitis, where diagnostic fashion or opportunity may exert influence. A rise in incidence of GP-recorded asthma between 1960 and 1990 in the UK may have reflected a shift in willingness to make this diagnosis because of new tests and treatments [1]. In the 1970s the commonest code related to the back in UK general practice was ‘‘osteoarthritis of the spine”, a label now all but replaced by ‘‘back pain” [6]. Completeness of recording. GPs will not record everything. Presented with multiple problems during an encounter, only the most ‘‘significant” or newest may be recorded. This may result in underestimates of period prevalence, particularly for chronic diseases. What is important is that at least one code is entered at each patient contact, since most chronic or episodic problems
0304-3959/$34.00 Ó 2008 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.pain.2008.04.015
470
Editorial / Pain 137 (2008) 469–470
presented to the GP should eventually appear in the records. Incidence. Identification of incident cases of pain syndromes, as in Dieleman’s study, contributes important information because primary care is where people take new pain. Apart from special surveillance schemes (e.g. in occupational settings), there are few alternative places to obtain such data. However, for many persons with common pain problems, the trip to the GP will not concern the ‘‘first ever occurrence” so central to the epidemiology of cancer or cardiovascular problems. It will be about a ‘‘new consulting episode”, often a recurrence or exacerbation. This can only be defined by the absence of recent consultations about the same problem, and may not represent the actual problem onset. Linking morbidities. Perhaps the strongest application of GP databases is investigation of linkages between different symptoms and diseases. The databases follow patients continuously over many years. Here is an opportunity to investigate the influence of comorbid illness on pain (as in Dieleman’s paper), and novel hypotheses like the inflammatory basis of chronic pain syndromes, or the extent to which pain is a red flag for serious underlying disease. Now that lifestyle characteristics such as weight and blood pressure are routinely checked and recorded, the databases also offer real-time monitoring of health status. Treatments. All prescribed treatments are recorded and the databases provide a picture of prescribing for pain syndromes [2,5]. Limitations exist. It is not always possible to tie a prescription to a particular morbidity, although use of controls [2] or date-matching with recorded morbidities offer possible solutions. The data represent ‘‘treatment that is prescribed in general practice”, and over-the-counter medication or private therapy is unlikely to appear. Other applications. Some studies are now linking consultation records to survey data in the same populations. By comparing persons who do and do not consult, outcomes of consultation or barriers to seeking help for pain problems can be investigated. Information not routinely recorded in primary care but available from surveys, such as functional limitation, can be linked to the more dynamic consultation data. GP databases can be used for follow-up measures in large scale population studies such as the UK Biobank project (500,000 people with bloods taken for genetic
analysis) [3]. Nested case-control analyses (see [2]), comparing those who do and do not consult about a pain syndrome, will be an efficient method in Biobank to investigate gene–environment interactions causing pain or determining response to treatment. Conclusion. As GPs in many health care systems are increasingly required to record higher quality and more comprehensive information for audit of care and payment purposes, so databases will be more commonly used for research. Even with the caveats discussed above, this type of information is the best available for routinely monitoring the occurrence and course of pain and health care in large populations. References [1] Anderson HR, Gupta R, Strachan DP, Limb ES. 50 years of asthma: UK trends from 1955 to 2004. Thorax 2007;62: 85–90. [2] Dieleman JP, Kerklaan J, Huygen FJPM, Bouma PAD, Sturkenboom MCJM. Incidence rates and treatment of neuropathic pain conditions in the general population. Pain 2008;137:681–8. [3] Elliott P, Peakman TC. The UK Biobank sample handling and storage protocol for the collection, processing and archiving of human blood and urine. Int J Epidemiol 2008;37:234–44. [4] Gore M, Dukes E, Rowbotham DJ, Tai KS, Leslie D. Clinical characteristics and pain management among patients with painful peripheral neuropathic disorders in general practice settings. Eur J Pain 2007;11:652–64. [5] Linsell L, Dawson J, Zondervan K, Randall T, Rose P, Carr A, et al. Prospective study of elderly people comparing treatments following first primary care consultation for a symptomatic hip or knee. Fam Pract 2005;22:118–25. [6] McCormick A, Fleming D, Charlton J. Morbidity statistics from general practice: fourth national study 1991–1992. London: HMSO; 1995. [7] Soriano JB, Maier WC, Visick G, Pride NB. Validation of general practitioner-diagnosed COPD in the UK General Practice Research Database. Eur J Epidemiol 2001;17:1075–80. [8] Taylor W, Smeets L, Hall J, McPherson K. The burden of rheumatic disorders in general practice: consultation rates for rheumatic disease and the relationship to age, ethnicity, and smallarea deprivation. N Z Med J 2004;117:U1098.
K.P. Jordan P. Croft Arthritis Research Campaign National Primary Care Centre, Keele University, Keele, Staffs ST5 5BG, UK Tel.: +44 1782 583924 (K.P. Jordan) E-mail address: [email protected] (K.P. Jordan)
Editorial
Opportunities and limitations of general practice databases in pain research
Dieleman et al.’s [2] investigation of neuropathic pain may trouble clinical pain specialists. It rides a little roughly over a clinician’s detailed approach to diagnosis and classification. The authors have based their research on one of an increasing number of databases drawn from primary care consultations. These are based on the routine recording and coding of illness and morbidity by family doctors or general practitioners (GPs) who do not necessarily use standard diagnostic labels for neuropathic pain syndromes in their daily practice. As with all forms of research data, such databases can be misused or misapplied. If their weaknesses are acknowledged and discussed, however, they have much to contribute to pain research. Dieleman’s paper provides an excellent example of how to use them carefully and creatively. Here we discuss some general issues. Measuring morbidity occurrence. In countries such as the UK and the Netherlands, general practices have a list of people from the general population registered for provision of primary care and access to secondary care. In such practices, morbidities are often routinely coded and recorded during consultations. Occurrence rates of morbidities can be calculated by relating the number of people consulting for a problem to the size and characteristics of the registered populations [4,8]. Hence GP databases are a source of routine statistics about morbidity occurrence. Such figures, however, will under-represent true occurrence in the population if not all cases are brought to the attention of a GP. This is a problem in health care systems with direct patient access to specialists, but even in countries with ‘‘gatekeeper” systems only a proportion of sufferers from common syndromes such as back pain will take them to their family doctor. So occurrence will relate to ‘‘pain for which consultation with the GP has been sought”. This matters less for conditions always seen by the GP, or when the objective is to measure health care use or to estimate associations with characteristics such as age and gender.
Labelling. Databases reflect what GPs choose to call things in usual clinical practice, and they do not usually incorporate standardised criteria for applying diagnostic labels. GPs work with uncertainty and early presentations; they watch for serious disease whilst accepting that symptoms are often undifferentiated when first presented. Many systems for coding morbidities, such as the International Classification of Primary Care, allow symptoms as well as definite diagnoses to be recorded. This is a big gain for epidemiology – better to have the big pool recorded (all labels relating to back pain, for example) than selected diagnoses made on spurious grounds. When there is a specific disease underlying presenting symptoms, this is likely to appear eventually in the GP record. Validation of database diagnoses for some ‘‘serious” diseases have been published. Dieleman provides one example of this; others have validated GP records against sources such as specialist records or assessments (e.g. [7]). Provided there is some validity and consistency when labels like carpal tunnel syndrome or trigeminal neuralgia are used, these datasets can be used for large-scale epidemiology research even if precision is lacking in individual patients. More difficult are diagnoses such as asthma or tenosynovitis, where diagnostic fashion or opportunity may exert influence. A rise in incidence of GP-recorded asthma between 1960 and 1990 in the UK may have reflected a shift in willingness to make this diagnosis because of new tests and treatments [1]. In the 1970s the commonest code related to the back in UK general practice was ‘‘osteoarthritis of the spine”, a label now all but replaced by ‘‘back pain” [6]. Completeness of recording. GPs will not record everything. Presented with multiple problems during an encounter, only the most ‘‘significant” or newest may be recorded. This may result in underestimates of period prevalence, particularly for chronic diseases. What is important is that at least one code is entered at each patient contact, since most chronic or episodic problems
0304-3959/$34.00 Ó 2008 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.pain.2008.04.015
470
Editorial / Pain 137 (2008) 469–470
presented to the GP should eventually appear in the records. Incidence. Identification of incident cases of pain syndromes, as in Dieleman’s study, contributes important information because primary care is where people take new pain. Apart from special surveillance schemes (e.g. in occupational settings), there are few alternative places to obtain such data. However, for many persons with common pain problems, the trip to the GP will not concern the ‘‘first ever occurrence” so central to the epidemiology of cancer or cardiovascular problems. It will be about a ‘‘new consulting episode”, often a recurrence or exacerbation. This can only be defined by the absence of recent consultations about the same problem, and may not represent the actual problem onset. Linking morbidities. Perhaps the strongest application of GP databases is investigation of linkages between different symptoms and diseases. The databases follow patients continuously over many years. Here is an opportunity to investigate the influence of comorbid illness on pain (as in Dieleman’s paper), and novel hypotheses like the inflammatory basis of chronic pain syndromes, or the extent to which pain is a red flag for serious underlying disease. Now that lifestyle characteristics such as weight and blood pressure are routinely checked and recorded, the databases also offer real-time monitoring of health status. Treatments. All prescribed treatments are recorded and the databases provide a picture of prescribing for pain syndromes [2,5]. Limitations exist. It is not always possible to tie a prescription to a particular morbidity, although use of controls [2] or date-matching with recorded morbidities offer possible solutions. The data represent ‘‘treatment that is prescribed in general practice”, and over-the-counter medication or private therapy is unlikely to appear. Other applications. Some studies are now linking consultation records to survey data in the same populations. By comparing persons who do and do not consult, outcomes of consultation or barriers to seeking help for pain problems can be investigated. Information not routinely recorded in primary care but available from surveys, such as functional limitation, can be linked to the more dynamic consultation data. GP databases can be used for follow-up measures in large scale population studies such as the UK Biobank project (500,000 people with bloods taken for genetic
analysis) [3]. Nested case-control analyses (see [2]), comparing those who do and do not consult about a pain syndrome, will be an efficient method in Biobank to investigate gene–environment interactions causing pain or determining response to treatment. Conclusion. As GPs in many health care systems are increasingly required to record higher quality and more comprehensive information for audit of care and payment purposes, so databases will be more commonly used for research. Even with the caveats discussed above, this type of information is the best available for routinely monitoring the occurrence and course of pain and health care in large populations. References [1] Anderson HR, Gupta R, Strachan DP, Limb ES. 50 years of asthma: UK trends from 1955 to 2004. Thorax 2007;62: 85–90. [2] Dieleman JP, Kerklaan J, Huygen FJPM, Bouma PAD, Sturkenboom MCJM. Incidence rates and treatment of neuropathic pain conditions in the general population. Pain 2008;137:681–8. [3] Elliott P, Peakman TC. The UK Biobank sample handling and storage protocol for the collection, processing and archiving of human blood and urine. Int J Epidemiol 2008;37:234–44. [4] Gore M, Dukes E, Rowbotham DJ, Tai KS, Leslie D. Clinical characteristics and pain management among patients with painful peripheral neuropathic disorders in general practice settings. Eur J Pain 2007;11:652–64. [5] Linsell L, Dawson J, Zondervan K, Randall T, Rose P, Carr A, et al. Prospective study of elderly people comparing treatments following first primary care consultation for a symptomatic hip or knee. Fam Pract 2005;22:118–25. [6] McCormick A, Fleming D, Charlton J. Morbidity statistics from general practice: fourth national study 1991–1992. London: HMSO; 1995. [7] Soriano JB, Maier WC, Visick G, Pride NB. Validation of general practitioner-diagnosed COPD in the UK General Practice Research Database. Eur J Epidemiol 2001;17:1075–80. [8] Taylor W, Smeets L, Hall J, McPherson K. The burden of rheumatic disorders in general practice: consultation rates for rheumatic disease and the relationship to age, ethnicity, and smallarea deprivation. N Z Med J 2004;117:U1098.
K.P. Jordan P. Croft Arthritis Research Campaign National Primary Care Centre, Keele University, Keele, Staffs ST5 5BG, UK Tel.: +44 1782 583924 (K.P. Jordan) E-mail address: [email protected] (K.P. Jordan)