key: cord-0027441-vfesslpm
authors: Yu, Dahai; Missen, Matthew; Jordan, Kelvin P; Edwards, John J; Bailey, James; Wilkie, Ross; Fitzpatrick, Justine; Ali, Nuzhat; Niblett, Paul; Peat, George
title: Trends in the Annual Consultation Incidence and Prevalence of Low Back Pain and Osteoarthritis in England from 2000 to 2019: Comparative Estimates from Two Clinical Practice Databases
date: 2022-02-17
journal: Clin Epidemiol
DOI: 10.2147/clep.s337323
sha: f3a6c6f5d7d30f0b1bdb645b9cbaa39a2b1fcaa5
doc_id: 27441
cord_uid: vfesslpm

PURPOSE: To compare estimates of annual person-consulting incidence and prevalence of low back pain (LBP) and osteoarthritis for two national English electronic health record databases (Clinical Practice Research Datalink (CPRD) Aurum and CPRD GOLD). PATIENTS AND METHODS: Retrospective, population-based, longitudinal cohort study. LBP and osteoarthritis cases were defined using established codelists in people aged ≥15 and ≥45 years, respectively. Incident cases were new recorded cases in a given calendar year with no relevant consultation in the previous 3 years (denominator = exact person-time in the same calendar year for the at-risk population). Prevalent cases were individuals with ≥1 consultation for the condition of interest recorded in a given calendar year, irrespective of prior consultations for the same condition (denominator = all patients with complete registration history in the previous 3 years). We estimated age-sex standardised incidence and annual (12-month period) prevalence for both conditions in 2000–2019, overall, and by sex, age group, and region. RESULTS: Standardised incidence and prevalence of LBP from Aurum were lower than those from GOLD until 2014, after which estimates were similar. Both databases showed recent declines in incidence and prevalence of LBP: declines began earlier in GOLD (after 2012–2014) than Aurum (after 2014–2015). Standardised incidence (after 2011) and prevalence of osteoarthritis (after 2003) were higher in Aurum than GOLD and showed different trends: incidence and prevalence were stable or increasing in Aurum, decreasing in GOLD. Stratified estimates in CPRD Aurum suggested consistently higher occurrence among women, older age groups, and those living in the north of England. CONCLUSION: Comparative analyses of two English databases produced conflicting estimates and trends for two common musculoskeletal conditions. Aurum estimates appeared more consistent with external sources and may be useful for monitoring population musculoskeletal health and healthcare demand, but they remain sensitive to analytic decisions and data quality.

Musculoskeletal disorders (MSD) are the main drivers of non-communicable disease disability burden in most countries and regions worldwide. 1 In England, they account for an estimated 21% of total years lived with disability (YLD), 2 6.2 million working days lost, 3 12-14% of all primary care consultations in people aged 15 years and over, 4, 5 and the third largest programme budget for NHS healthcare expenditure. 6 The need for better information for chronic disease surveillance of MSD has been highlighted by the Chief Medical Officer 7 and in successive Global Burden of Disease reports for England. 8, 9 Public Health England's 5-year strategy for musculoskeletal health (2019-2024) includes a commitment to high quality, accessible data and intelligence tools to support surveillance and reduce unwarranted variation of musculoskeletal conditions across the population pathway. 10 Aside from Global Burden of Disease-modelled estimates, national and subnational population profiles in England currently rely on a relatively narrow range of indicators derived from national population surveys such as Health Survey for England and the General Practice Patient Survey. 11 Primary care electronic health record (EHR) databases are underutilized but potentially important sources of data given their continuous nature, their size and population coverage, and the fact that the primary healthcare setting is where most cases of common, disabling MSDs present and are managed. These sources are already used for tracking annual estimates of the prevalence of osteoporosis and rheumatoid arthritis; conditions for which recording in UK general practice have been incentivised through the General Medical Contract. Low back pain, osteoarthritis, and other regional pain syndromes are the major contributors to population disability, but there are significant challenges in obtaining useful and robust estimates from primary care EHR databases for these conditions: their classification is typically less standardised; a multitude of symptom and diagnostic problem codes may be used by practitioners; completeness of recording has not been incentivised; only a proportion of sufferers may present to primary healthcare in a given period. Nor can these factors be assumed to be constant between subpopulations or over time. In previous studies, we found evidence of strong period effects and increasing underrecording of osteoarthritis diagnostic coding in a UK database. 12, 13 Despite these challenges, the rate at which new cases present to primary care, and the proportion of the population who consult for these MSDs represent potentially important indicators of demand for healthcare as well as measures of musculoskeletal health in the population that warrant investigation as part of a wider suite of population health indicators. The present study focussed on low back pain and osteoarthritis, which account for over half of all YLDs attributed to MSDs. We identified only four previously published studies of low back consultation prevalence 6,14-16 and eight reporting consultation incidence or prevalence estimates for osteoarthritis 12,14-20 derived from English primary care electronic health record data (Supplementary Data Tables S1-S4). National estimates for low back pain are either lacking or need updating, whereas for osteoarthritis, the most recent studies have reported an unexpected decline in annual incidence rates up to 2017. These studies have been based on the national Clinical Practice Research Datalink (CPRD GOLD) database, which has historically drawn data from general practices using the Vision ® software system. 21 Use of this system in English general practices, however, has been declining over time, resulting in CPRD GOLD coverage increasingly focussed on practices in Greater Manchester, Birmingham, London, and the south of England, 22 and only 50 contributing practices in England as of April 2021. 23 In response, CPRD launched the Aurum database in October 2017 24 which extracts data from general practices using the EMIS Web ® software system, now used by over half of English general practices. 

In this study, we compare national estimates and trends obtained from CPRD Aurum and CPRD GOLD for the annual person-consulting incidence and prevalence of low back pain and osteoarthritis for England over the 20-year period spanning 2000-2019 as there was strong period effect before 2000 in CPRD GOLD identified in our previous study. 16 Then, using data from the larger CPRD Aurum database, we provide new estimates of the above, stratified by age, sex, and region.

A retrospective, population-based, longitudinal cohort study was implemented to estimate both annual incidence and prevalence between 2000 and 2019 using English primary care electronic health record databases.

CPRD GOLD and Aurum are complementary databases including anonymised data from patient electronic health records in primary care on demographics, diagnoses, symptoms, prescriptions, referrals, immunizations, lifestyle factors, tests and results. Patient-level data linkages to national secondary care databases, disease registries, death registrations and deprivation measures are available for both. Practices contributing to GOLD undertook training in morbidity coding and needed to reach an up-to-standard recording mark. Up-to-standard dates were not yet available within Aurum at the time of our study. 25 Both CPRD GOLD and Aurum are available to researchers worldwide although at a cost. To access the CPRD database, researchers should follow the process from CPRD (https://www.cprd.com/research-applications).

As of April 2021, CPRD GOLD included data on 20 million patients from 964 practices across the UK, of whom 3.1 million were active and current contributors (5% of the UK population). 23 As of February 2021, CPRD Aurum included data on 39.7 million patients from 1489 practices, of whom 13.3 million were alive and current contributors (20% of the population of England). 26 In the current study, we included CPRD Aurum practices known to have switched from using Vision ® software, ie, we permitted overlapping patient and practice membership between GOLD and Aurum analyses. For example, based on the 'VisionToEmisMigrators' file, 14.1% of Aurum practices contributing data to low back pain prevalence estimates also contributed data to estimates in GOLD.

In UK primary care, symptom and diagnosis problems have historically been recorded using Read codes. SNOMED codes began to replace Read codes from April 2018. Practices using EMIS Web ® can also use local EMIS codes. High levels of validity across a range of diagnostic coding have been previously reported within CPRD 27 and further supporting evidence of diagnostic validity within Aurum is emerging. 28, 29 Using established Read codelists (codelists available from www.keele.ac.uk/mrr), and with reference existing clinical practice guidelines and previous consensus exercises, 30, 31 we defined cases of non-specific low back pain as having at least one clinical event with a recorded diagnosis of low back pain in persons aged 15 years and over within a given calendar year. Osteoarthritis cases had at least one clinical event with a recorded diagnosis of osteoarthritis (N05."Osteoarthritis and allied disorders") in persons aged 45 years and over within a given calendar year. A single record of a relevant code within the primary care EHR within a calendar year of interest, and other similar definitions, have been used in previous studies 6,12,14-20,32-41 and have generally higher sensitivity but lower specificity than more restrictive algorithms requiring multiple records. 42 

To determine annual prevalence, our denominator population was all patients with complete registration history for the previous three calendar years. For the calculation of annual incidence, they also had to have no coded record of the condition of interest (low back pain, osteoarthritis) in those 3 years. The numerator population was all patients within the denominator population who had a coded record of the condition of interest during the year examined. Estimates are sensitive to the "look back period" and method chosen to exclude prevalent cases. 12 From previous analyses, a three-year "look back period" to exclude prevalent cases appears to be optimal for several common musculoskeletal disorders and across multiple years. 12 (Illustrative examples of the selection of numerator and denominator for incidence of low back pain incidence and prevalence are provided in Supplementary Data Figures S1 and S2).

Annual person-consultation incidence and prevalence, expressed per 1000 person-years, were produced for the period 2000-2019 in CPRD Aurum and separately in CPRD GOLD. Incidence and prevalence were calculated as the number of cases with one or more relevant recorded clinical events in the calendar year divided by the total person-time of followup in the at-risk population for that calendar year. Person-time was censored by the earliest of the following outcomes: relevant consultation, death, transfer/de-registration from contributing practice, or 31 December. Age-sex-standardized incidence and prevalence were estimated using the mid-2019 England population (ONS code: E92000001) as the standard with 95% confidence intervals estimated by Poisson regression. To explore changes over time in the overall trends of incidence and prevalence in CPRD GOLD and Aurum, we performed joinpoint analyses using the Joinpoint regression program (version 4.9.0.0, Statistical Research and Applications Branch, National Cancer Institute, 2021). Annual percentage changes in standardised incidence and prevalence were estimated in each period segment defined by the joinpoints. The number of joinpoints (0--3) selected for each model was based on optimal value of the Bayesian Information Criterion.

To explore the possibility of simplified prevalence estimation, we repeated prevalence estimates but removing the requirement for 3 years of prior complete registration for both numerator and denominator.

The study was approved by the Independent Scientific Advisory Committee for CPRD research (protocol reference: 20_054R). No further ethical permissions were required for the analyses of these anonymized patient-level data.

There was no patient or public involvement in the study.

The size of the available at-risk population within Aurum grew steadily between 2000 and 2019 to reach over 10 times the size of GOLD in 2019 (eg, for low back pain prevalence estimation, the denominator was 7,274,733 in Aurum vs 704,293 in GOLD). The size of the at-risk population in GOLD for our estimates peaked in 2008-2010 (eg, 2,619,616 in 2010 for low back pain prevalence estimation; see Supplementary Data Tables S5-S8).

Age-sex standardised estimates from Aurum of annual consultation incidence and prevalence for low back pain and osteoarthritis rose sharply 

Annual consultation incidence and prevalence of low back pain were consistently higher in women than in men ( Figure 2 ) and increased with age peaking at 75-84 years (Supplementary Data Figures S3 and S4 ). 

There were regional disparities, with low back pain incidence and prevalence consistently higher in northern than southern regions of England (Supplementary Data Figures S5 and S6 ).

As with low back pain, annual consultation incidence and prevalence of diagnosed OA were consistently higher in women than in men ( Figure 3 ) and increased with age, peaking at 75-84 years (Supplementary Data Figures S7 and S8 ). Consultation incidence and prevalence of osteoarthritis were consistently higher in northern regions of England than in the south (Supplementary Data Figures S9 and S10 ).

Relaxing the requirement for 3 years of prior registration for prevalence estimation resulted in slightly lower prevalence estimates but the same underlying trends (Supplementary Data Tables S9 and S10; Figures S11-S16).

Despite applying a consistent approach to case definitions and methods of analysis, we observed important differences in estimates of the annual consultation incidence and prevalence of low back pain and osteoarthritis between 2005 and 2019 obtained from two English national databases -CPRD Aurum and GOLD databases. While estimates from Aurum suggested little or no overall change in the age-sex-standardised consultation incidence and prevalence of low back pain in 2019 compared to 2005, and modest increases in osteoarthritis over this period, estimates from GOLD suggested substantial decreases.

Our findings extend those obtained in a comparative analysis of UK primary care databases over a decade ago that showed that different databases yielded a (sometime wide) range of estimates of the annual consultation prevalence and incidence of common musculoskeletal pain conditions. 17 We show that they can also produce conflicting trends over time. This phenomenon does not apply to all conditions and outcomes. For example, a recent study by Gulliford et al 43 found very similar rates of antibiotic prescribing from CPRD GOLD and Aurum, albeit limited to a single year of interest. The precise reasons for the differences in trends seen in the current study are unclear. They cannot be attributed to differences between GOLD and Aurum in their geographic coverage (differences exist within regions, data not shown) or to the introduction of the new SNOMED coding system that replaces Read codes (SNOMED began to be implemented in 2018 and would affect both Vision and EMIS systems). In previous studies, an unexpected decrease or lack of increase in annual osteoarthritis consultation incidence rates is reversed if a broader case definition is used, implying a shift in coding behaviour over time from diagnostic to symptom coding. 19, 20 However, it is not clear why this should affect GOLD more than Aurum. If practices with higher levels of non-incentivised problem/diagnostic coding were more likely to switch from Vision to EMIS (or other IT system), this may contribute to the observed trends in GOLD estimates, but we did not directly test this.

Irrespective ). Yet it must be recognised that the Aurum annual estimates reflect expressed demand within a given calendar year for primary healthcare that is accessible through general practice. For instance, the one-year period prevalence of low back pain in the adult population is likely to exceed 30%, 46 with activity-limiting or chronic low back pain being expected to be approximately 12-18%. 46, 47 This contrasts with an estimated annual consultation prevalence of 4-5% from the current Aurum estimates, confirming that the majority of low back pain in the adult population in a given calendar year is not presented to general practice and recorded in the structured EHR.

After allowing for differences in the age of the target population, our estimate of the annual consultation incidence of osteoarthritis of 16-19 per 1000 person-years in adults aged 45 years and over from Aurum is broadly consistent with estimates of 6-10 per 1000 person-years in all ages obtained from previous analyses of CPRD and other local and national UK primary care EHR databases. 12, 19, 20 Comparison of consultation prevalence estimates for osteoarthritis is more difficult due to the use of different period prevalences (5-year, 18 7-year, 16 ever 19 ) and target populations (all ages, 14, 16, 18 15+, 17 20+, 19 45+, 16 65+ 15 years). Where direct comparison is possible, our current Aurum estimates appear to fall between those from previous local 16 and national database studies. 19 We found no previously published comparable consultation incidence estimates for LBP from UK EHR data sources. Several previous prevalence studies have used narrow case definitions (eg, intervertebral disk disorder) which cannot be directly compared. However, our current Aurum estimates for annual consultation prevalence of low back pain are lower than three previous UK studies using a similar definition. 14, 16, 17 Together, these comparisons suggest that the annual consultation prevalence estimates from the current study are likely to be conservative, although there is no reason to believe that this should result in systematic bias in monitoring trends over time.

Occurrence estimates for chronic health condition obtained from dynamic EHR data are typically sensitive to the specific case definition adopted, the period and analytic approach used to distinguish incident from prevalent cases, the capture and linkage of hospital data and other data sources, changing population structure, and the particular characteristics and incentives for coding behaviour within a healthcare system or database. 48 The codelists used in this study built on previous mapping and consensus involving general practitioners. The future use of routinely recorded data to monitor the rate of new and existing cases of musculoskeletal disorders presenting to general practice still requires care due to the large number of available codes and variations in coding behaviour. The encouragement of practitioners to use a smaller set of preferred codes and periodically reviewing and revising codelists used to define cases may help. We have justified the choice of look-back period by previous empirical work. 20 Our study period preceded any COVID-19 impacts on musculoskeletal health and accessing primary healthcare. We focused our interpretation on estimates from after 2004, having observed sharp increases in 2000-2003. In a previous analysis of another national GP database -The Health Improvement Network (THIN) -Horsfall et al 49 incidence estimates across a range of outcomes were highly sensitive to the application of different data quality filters, including acceptable computer usage levels. While the effects of this appeared to lessen after 2003, variations in data quality between practices and across time in a dynamic population may still be a source of bias. For example, acceptable computer usage was previously defined by primary care physician entries, but musculoskeletal consultations are likely to be increasingly with non-medical staff such as nurse practitioners and physiotherapists. The level of coding of this activity is less clear. Our analyses are based on the structured primary care EHR without access to unstructured (free text) data or linkage to hospital record data. The findings of this study are limited to UK primary care. This study has focussed on incidence and prevalence of musculoskeletal conditions. Other studies have shown closer agreement in estimates obtained from the two databases, for example in characteristics of patients recorded with chronic obstructive pulmonary disease 50 and antibiotic prescribing rates. 43 Further research is needed to assess comparability of incidence and prevalence of other health conditions between GOLD and Aurum, and findings from other types of research study.

Our study demonstrates some important differences between CPRD GOLD and Aurum databases in estimates of the consultation incidence and prevalence of common, disabling musculoskeletal pain conditions. Estimates from Aurum appeared to be more consistent with external sources. As indicators for monitoring musculoskeletal health in populations, they are likely to be a valuable addition to existing population estimates obtained from periodic national self-report surveys, but sensitive to analytic decisions and data quality.

Data may be obtained from a third party and are not publicly available. The data were obtained from the Clinical Practice Research Datalink (CPRD). CPRD data governance does not allow us to distribute patient data to other parties. Researchers may apply for data access at http://www.CPRD.com/research-applications. Our approved study protocol is available on request, and codelists are freely available at https://www.keele.ac.uk/mrr/codelists/.

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online journal focusing on disease and drug epidemiology, identification of risk factors and screening procedures to develop optimal preventative initiatives and programs. Specific topics include: diagnosis, prognosis, treatment, screening, prevention, risk factor modification, systematic reviews, risk & safety of medical interventions, epidemiology & biostatistical methods, and evaluation of guidelines, translational medicine, health policies & economic evaluations. The manuscript management system is completely online and includes a very quick and fair peer-review system, which is all easy to use

This study is based on data from the Clinical Practice Research Datalink obtained under licence from the UK Medicines and Healthcare Products Regulatory Agency. The data are provided by patients and collected by the NHS as part of their care and support. The interpretation and conclusions contained in this study are those of the authors alone. This work was supported by funding from Public Health England. KPJ is also supported by matched funding awarded to the NIHR Applied Research Collaboration (West Midlands).

The authors have no conflicts of interest to declare.