Pediatric chronic pain, defined as pain that persists or recurs over ≥3 months, is associated with functional limitation, high out-of-pocket health care expenditures, and high rates of emergency care utilization.1–5 Multidisciplinary chronic pain clinics have sought to improve the management of chronic pain in children whose pain is not adequately managed by primary or specialty care providers.6,7 Despite accumulating evidence for the efficacy of dedicated chronic pain programs,6–9 some data suggest that referral to these programs may be delayed and subject to socioeconomic disparities. Prior studies indicated that children’s chronic pain persisted between 8 months and 3 years before referral to an outpatient chronic pain clinic;4,10–13 and that socioeconomically disadvantaged children were underrepresented among patients seen by a pediatric chronic pain clinic.14 However, these studies were limited to describing the characteristics of children who have been referred to a chronic pain clinic, and could not precisely define the factors associated with the likelihood of referral.4,10–14 Although nationally representative data have been used to describe the association between pediatric chronic pain and the use of primary care, mental health care, and emergency care,1 the incidence and predictors of referral to a dedicated chronic pain program among children with chronic pain are not well understood.
Most children with chronic pain see a primary care physician at least once a year, and most chronic pain is managed in the primary care setting.1,15 However, referrals to pediatric chronic pain clinics are most commonly made by specialists. Specialists rather than general practitioners refer 54% to 66% of children seen by a specialized pain clinic, according to recent studies.4,10,12 Previous studies have suggested that referrals to a chronic pain clinic may be influenced by socioeconomic factors such as place of residence and type of health insurance coverage,10,14 and that the recognition and management of pediatric pain may be dependent on patients’ race/ethnicity.16–18 On the basis of our experience, we also speculate that referral likelihood may be dependent on the type of chronic pain, associated surgeries or trauma, or provider differences in referring patients to this service.
Without specific data on the rates and predictors of referral to chronic pain services among a population or sample of children with chronic pain, the impact of these possible barriers to care cannot be accurately defined. Therefore, analyzing the rate of referral to a chronic pain clinic can help identify patient characteristics associated with lower likelihood of referral, and thereby improve access to this service for children with chronic pain, potentially reducing the long duration of pain symptoms previously described among patients presenting to similar clinics. In this study, we retrospectively reviewed data from a large hospital health system to identify outpatient visits by adolescents presenting with chronic pain. Our primary aim was to estimate the likelihood of subsequent referral to our outpatient chronic pain clinic. Our secondary aim was to describe factors associated with chronic pain clinic referral among adolescents who present with chronic pain at an outpatient visit to their primary care pediatrician (PCP) or a pediatric specialist.
MATERIALS AND METHODS
This study was approved by the Institutional Review Board (IRB) at Nationwide Children’s Hospital (NCH) with a waiver of individual consent. We retrospectively queried electronic medical records to identify adolescents of 13 to 18 years old visiting any outpatient clinic in the NCH health system between January 2010 and September 2015. International Classification of Diseases, Ninth revision (ICD-9) codes, described in a previous study,19 were used to identify outpatient visits where patients presented with chronic pain. We selected visits that had a diagnosis or problem list ICD-9 code included in the following list: 307.89 (psychogenic pain, not otherwise specified/psychogenic pain, not elsewhere classified [NEC]), 337.20 (reflex sympathetic dystrophy [RSD], not otherwise specified), 337.27 (RSD, upper limb/arm), 337.22 (RSD, lower limb/leg), 337.29 (RSD, NEC), 338.29 (chronic pain, NEC), 338.4 (chronic pain syndrome), 354.4 (complex regional pain syndrome [CRPS]/causalgia of upper limb), or 355.71 (CRPS/causalgia lower limb). All other ICD-9 codes for selected visits were also reviewed to identify pain complaints which may have not been included in this list (for example, a significant proportion of patients also had ICD-9 codes for abdominal pain).19
All ICD-9 codes for pain problems obtained on our data query were classified according to the predominant categories in our cohort (musculoskeletal pain, abdominal pain, regional pain syndrome, and generalized chronic pain [eg, presence of code 338.29 for chronic pain NEC, with no further information on pain location available from other ICD-9 codes]), and these categories were not mutually exclusive. Because we aimed to identify a cohort of adolescents already being served our institution, and for whom our pain clinic would be geographically convenient, we excluded patients who lived outside of Franklin County (where the primary NCH campus is located) or one of its contiguous counties. (The next-closest hospital-based pediatric chronic pain clinic is 3 counties and ~70 miles away from NCH.) Visits resulting in admission and overnight stay were excluded, although patients with such visits may have still been included in the study if one of their outpatient visits was associated with a chronic pain diagnosis code. For each patient, the index encounter was defined as the earliest outpatient visit in another clinic, which was associated with one of the prespecified chronic pain diagnosis codes (detailed above). Patients who had been referred to our chronic pain clinic before this index encounter were excluded from analysis.
The primary study outcome was a referral to the outpatient chronic pain clinic at NCH, whether this referral occurred following the index encounter, or at a later time. The clinic was established in 2007 and we began the review period in 2010 to exclude the initial period when the referral rate could have been low due to lack of familiarity with this service. Because of the retrospective nature of the study, referrals to the chronic pain clinic were tracked through December 2017, before the time the study was submitted for IRB approval. The chronic pain clinic at NCH serves children and adolescents up to the age of 18, providing a 4 to 6 month program of outpatient visits where patients are treated using an integrative approach, which includes medical management, psychological interventions, physical therapy, and complementary therapies such as massage therapy and acupuncture. The specific duration of treatment and therapies used are determined in consultation with the patient and family. The clinic was founded as a multidisciplinary service and the only significant change in practice during the review period was the opening of another clinic location in June 2015, allowing for 2 additional clinic sessions per week. All patients served by this clinic are referred by another provider. Data on referrals to the chronic pain clinic were obtained from a quality improvement (QI) database maintained by this service. Of note, not all referred patients completed a clinic intake visit, and not all patients beginning treatment completed the planned treatment course.
Predictors of chronic pain clinic referral were assessed at the index encounter (in another outpatient clinic) and included patient age, sex, race/ethnicity, health insurance type (commercial, Medicaid, or other), and type of clinic visited. As a further measure of socioeconomic status (SES), we used an index of socioeconomic disadvantage in the ZIP code of residence, based on American Community Survey data and incorporating median household income; median value of housing units; percentage of households receiving interest, dividend, or net rental income; percentage of adults of age 25 years and older who had completed high school; percentage of adults 25 years and older who had completed college; and percentage of employed people 16 years and above of age who were in management, business, science, or arts occupations.20–22 This index was divided into quartiles where the bottom quartile represented the most disadvantaged ZIP codes in Ohio. Chronic pain diagnosis and comorbidities noted at the index encounter were also evaluated. Comorbidities were assessed by a manual review of all ICD-9 codes recorded at the index encounter (excluding codes representing pain problems), and those comorbidities having >10% prevalence in the study cohort were grouped together for inclusion in the analysis. The comorbidity groups used in the analysis were musculoskeletal, mental health (most commonly, anxiety, depression, or attention-deficit/hyperactivity disorder), respiratory, gastrointestinal, and skin conditions. In the 12 months before the index (outpatient) encounter, we also determined whether patients had any emergency department (ED) visits, any surgeries (excluding procedures associated with ED admission), or any hospitalizations (excluding hospitalization through the ED or hospitalization associated with a surgical procedure); and whether they presented with a pain problem at any of these recent hospitalizations or ED visits.
Continuous data were summarized as medians with interquartile ranges, and categorical data were summarized as counts with proportions. In the descriptive analysis, we stratified patients according to whether they were ultimately referred to the chronic pain clinic, and according to the type of clinic they visited at the index encounter (PCP vs. specialist). Data were compared between subgroups using rank-sum tests or χ2 tests, as appropriate. Multivariable analysis of study outcomes was performed using logistic regression, with a stepwise forward selection of covariates at a threshold of P<0.2. Data analysis included all patients meeting study inclusion and exclusion criteria, as outlined above, and no a priori power analysis was performed. Analyses were performed using Stata/IC 14.2 (StataCorp, LP, College Station, TX), and 2-tailed P<0.05 was considered statistically significant.
We identified 810 adolescents as potentially eligible for inclusion in our primary analysis, based on living near the hospital and having had an outpatient visit with a diagnosis of chronic pain during the 2010 to 2015 review period. For these patients, we retained the earliest encounter matching inclusion criteria. We then excluded 32 patients who had been previously referred to the chronic pain clinic. The final analytic sample included 778 patients (209/569 male/female; median age 15 years [interquartile range, 14 to 17], of whom 775 had complete data on study covariates for multivariable analysis. In this cohort, 96 (12%) patients were subsequently referred to the chronic pain clinic, after a median period of 3 months (interquartile range, 0 to 17 mo). (Among 259 patients who were excluded from our primary analysis solely due to living too far away from the hospital, 32 [12%] had been referred to the chronic pain clinic.) In the primary cohort of 778 patients, we found that during the 12 months before the index encounter in another outpatient clinic, 29% of patients had been admitted to the ED, 10% had undergone surgery, and 22% had been admitted for overnight hospitalization. Among 200 patients (26% of the primary study cohort) at least one recent ED visit or hospital admission was associated with a pain problem.
In Table 1, patient characteristics at the index encounter are compared between patients who were subsequently referred to the chronic pain clinic and patients who were not. The most common pain diagnosis among patients eventually referred to the chronic pain clinic was a generalized pain (N=401, 52%). There were also 61 patients with regional pain syndromes (8%). Other common pain problems in this group included localized musculoskeletal pain (27%) and abdominal pain (17%). When comparing our classification of pain problems to free-text data recorded in the clinic QI database (available for referred patients only), we found high concordance of musculoskeletal pain diagnoses (20/26 cases matching) and abdominal pain diagnoses (13/16 matching), but low concordance of regional pain diagnoses (5/15 matching), although the latter may have been explained by lack of standardized recording of CRPS (eg, a free-text note of “leg pain” in the QI database as opposed to an ICD-9 code of 355.71 for CRPS of the lower limb, in the primary analysis). Free-text pain problem descriptions for 56 referred patients in the “generalized chronic pain” category (who did not have a pain-related ICD-9 code specifying the location of pain) included 28 cases where patients were noted in the clinic database to have “body pain,” “global pain,” unspecified “chronic pain,” pain in multiple locations, fibromyalgia, or pain amplification syndromes. Among other referred patients in this category, the pain problem recorded in the pain clinic QI database was most commonly back pain (n=11 with no other pain complaints noted).
Twenty percent of referred patients were diagnosed with chronic pain at a PCP visit, compared with 23% who visited a sports medicine or physical therapy clinic, 14% who visited the adolescent medicine clinic, and 9%, 8%, and 6% who were seen by a rheumatologist, surgeon, or gastroenterologist. When stratifying the cohort by the type of provider seen at the index encounter, (Table 2) 14% of patients initially seen by a specialist were eventually referred to the chronic pain clinic, compared with 8% of patients who initially presented with chronic pain to a PCP. Patients diagnosed with chronic pain in a specialty clinic were more likely to be female and non-Hispanic white, more likely to use commercial insurance and reside in a higher-SES ZIP code, and more likely to have generalized chronic pain or regional pain syndromes, as opposed to localized musculoskeletal pain.
The multivariable logistic regression model predicting referral to the chronic pain clinic is shown in Table 3. The presence of generalized chronic pain (adjusted odds ratio [aOR], 1.8; 95% confidence interval [CI], 1.1-3.1; P=0.023), regional pain syndromes (aOR, 3.1; 95% CI, 1.5-6.7; P=0.003), mental health comorbidity (aOR, 3.0; 95% CI, 1.8-5.2; P<0.001), and musculoskeletal comorbidity (aOR, 1.9; 95% CI, 1.1-3.1; P=0.015) were associated with increased likelihood of referral to the chronic pain clinic. Female patients were more likely to be referred as compared with male patients (aOR, 2.0; 95% CI, 1.1-3.7; P=0.019). Recent surgeries and hospitalizations were also associated with increased likelihood of referral to the chronic pain clinic. However, the presence of a pain diagnosis code at a recent ED visit or hospitalization was not statistically significantly associated with this outcome in the adjusted model. There were no differences in the likelihood of referral according to the type of health insurance coverage, or the SES score in the patient’s ZIP code of residence. A difference in referral likelihood by race was only found on bivariate descriptive analysis (Table 1), but this variable did not meet the statistical significance threshold for inclusion in the multivariable model (Table 3).
A growing number of centers have reported success with using interdisciplinary outpatient clinics to manage pediatric chronic pain.4,10–14 Nevertheless, patterns of referral to pediatric chronic pain clinics are not well understood, in part because most research in this area is limited to samples of patients who have already been seen by these services. We retrospectively evaluated a cohort of adolescents considered potentially eligible for referral to our chronic pain clinic, whom we identified through a search of outpatient encounters at other clinics associated with ICD-9 codes indicating chronic pain. Among this cohort, we found that 12% of patients were eventually referred to our chronic pain clinic, with generalized chronic pain, regional pain syndromes, and the presence of musculoskeletal or mental health comorbidities increasing the likelihood of referral. We also found significant sex differences in the likelihood of referral to the chronic pain clinic, with male patients being less likely to be referred than female patients. Given the long duration of pain previously described among children presenting to a chronic pain clinic, our data can inform efforts to increase referral to this service for patients with chronic pain who could benefit from specialized interdisciplinary pain management.
Referral to a specialized multidisciplinary chronic pain service may be indicated when pediatric chronic pain proves refractory to initial treatment,23,24 or when it is accompanied by comorbidities complicating the formulation of a pain management plan. However, patterns of referral may depend upon the services offered by the chronic pain program (eg, outpatient management vs. intensive inpatient rehabilitation), other services’ approach to pain management, and individual provider variation. Several studies have argued that a long duration of pain symptoms and consultation with multiple specialists before chronic pain clinic referral suggest underutilization of specialized chronic pain services.10,11 In our analysis of adolescents diagnosed with chronic pain, only 12% were ultimately referred to our chronic pain clinic, yet median time to referral was relatively short (3 mo) in this group. After multivariable adjustment, we found that the type of pain and presence of comorbidities were more strongly associated with the likelihood of referral than the service at which chronic pain was diagnosed. Specific steps to improve the referral rate may be dependent on the resources and location of each institution, so our primary recommendation is that chronic pain clinics should identify the patient population whom they are able to serve, and, within this population, track the referral rate (not only the total number of referrals) as a process measure to inform QI initiatives in this area.
Previous studies have shown variation between centers in the predominant type of pain among children seen by the chronic pain service. In some centers, these clinics primarily serve patients with musculoskeletal pain,4,10,12,25 whereas in other centers, headaches were the most common pain problem in the chronic pain clinic.11,13 In our study, a significant number of patients referred to the chronic pain clinic had CRPS, a syndrome characterized by regional pain, which often starts from a distal limb. CRPS is associated with a wide variety of motor and autonomic disturbances, and may develop from a prior trauma or surgery.26 Multimodal treatment for CRPS in children is recommended, including cognitive-behavioral therapy and physical therapy,27,28 which may explain a high likelihood of referral to a multidisciplinary chronic pain service among these patients. More broadly, challenges of managing generalized or regional chronic pain may influence providers in other specialties to refer patients to a dedicated chronic pain clinic. The integration of psychological assessment and intervention in our clinic may also explain the higher odds of referral seen for patients with comorbid mental health conditions.
Recent studies have consistently described patients presenting to pediatric chronic pain clinics as overwhelmingly female, ~12 to 15 years of age, and, in the United States, primarily White.10–14,25,29,30 A prior study has considered the high representation of girls on the pediatric chronic pain service as potentially related to sex differences in severity of pain symptoms, or sex differences in seeking treatment for chronic pain,11 consistent with survey data showing pain to be more common among girls than boys.1,31 Although our study did not elucidate the specific mechanism, we found that girls with one of the included chronic pain diagnoses were more likely than boys to be referred to our chronic pain clinic. This may indicate a need for greater attention to the possibility of sex bias in assessing adolescents with chronic pain and determining whether they may benefit from chronic pain clinic services.
The lower likelihood of referral to the chronic pain clinic among Black adolescents on bivariate descriptive analysis (Table 1) may be related to implicit bias in diagnosing and managing pain in Black as compared with White patients,16,17 cultural differences in parental reaction to children’s chronic pain,18 or lower access to specialty health care providers. However, this difference by race was not found in the multivariable analysis, where race was excluded as a covariate in the stepwise covariate selection algorithm. Furthermore, while prior research has described socioeconomic barriers to use of pediatric chronic pain services,10,14,32 we did not find differences in the likelihood of referral to our chronic pain clinic by patients’ type of health insurance, or by the SES score of patients’ ZIP code of residence. This finding may be related to our sample inclusion criteria, limited to patients who already had been seen in our hospital’s clinics, and lived near the hospital main campus. Furthermore, our study was not designed to identify SES disparities earlier in the process of diagnosing and treating chronic pain, particularly disparities in whether pediatric chronic pain remains undiagnosed, precluding the possibility of referral to a pain service.
Pediatric chronic pain is associated with high health care utilization, including the high use of emergency care.1 Therefore, research evaluating the efficacy of pediatric chronic pain services has frequently focused on the reduction of health care utilization as a key outcome of chronic pain treatment.29,32,33 In our cohort of adolescents with chronic pain, we found high ED use within the 12 months before the initial visit to another outpatient clinic (29%), similar to results from a recent national survey, where 35% of children with significant chronic pain had visited the ED in the previous year.1 However, in the adjusted analysis, recent hospitalizations and surgeries, but not recent ED visits, were associated with increased likelihood of referral to our chronic pain clinic. As recent evidence shows reduced ED utilization after treatment of chronic pain in an interdisciplinary clinic,32 increasing referrals to chronic pain services—especially for patients with multiple ED visits or hospitalizations—may help reduce the high rate of emergency care utilization seen among adolescents with chronic pain in our study.
Although our study demonstrates a novel approach to quantifying predictors of referral to a pediatric chronic pain clinic, our conclusions are limited by some aspects of the data and methodology. First, our analysis was a retrospective database review which relied on a limited set of ICD-9 codes to identify adolescents with chronic pain. We selected these codes based on a previous study using administrative data to identify chronic pain in hospitalized children,19 and checked their applicability to our population by searching for encounters with these ICD-9 codes among patients who were actually seen in the chronic pain clinic. We were able to confirm that most of the patients seen in our chronic pain clinic during the study period indeed had an encounter with one of these ICD-9 codes entered in the medical record. Nevertheless, our inclusion of patients based on a limited set of ICD-9 codes likely underestimated how many children could have been considered for chronic pain clinic referral, and our results may not be generalizable to adolescents with other chronic pain problems, such as chronic headaches, who were not captured in our sample. Using an expanded definition of a population of children with chronic pain may reveal additional or different predictors of chronic pain clinic referral. We suggest that further studies should adapt the present methodology to a broader range of chronic pain diagnosis codes, to provide a more complete overview of pain clinic referral among adolescents with chronic pain.
Furthermore, our analysis was limited to patients residing near the main campus of a single hospital health system, meaning that we did not evaluate referrals from external providers, or referrals of patients living further away from NCH. We focused on referrals to an outpatient chronic pain clinic, but a similar approach may be undertaken to examine referral relationships with child and adolescent psychiatry, or an inpatient pain rehabilitation program if one is present. We also could not evaluate hospitalizations or ED visits to facilities outside the NCH system. A multi-institutional database on health care visits among adolescents with chronic pain would permit expanding this analysis of referrals to specialized chronic pain services, and better understanding outcomes associated with center-specific referral practices. Because of the retrospective nature of the study, we lacked standardized data on pain severity and functional limitation before pain clinic referral, and data on parental characteristics such as educational attainment and relationship status. Lastly, we analyzed referrals to our outpatient chronic pain clinic, whereas future research may similarly consider what factors influence referral to inpatient pain rehabilitation programs.33–35
The documented successes of multidisciplinary pediatric chronic pain clinics have raised new questions about whether these services are sufficiently and equitably available to children with chronic pain. In our retrospective review, we have described the rate of referral to our chronic pain service among a cohort of adolescents presenting with chronic pain to other outpatient clinics in the same health system. Referrals to the chronic pain clinic appear more likely for patients with generalized chronic pain or regional pain syndromes, and patients with mental health comorbidities who may benefit from the integration of psychological care with medical management and complementary therapies. Considering demographic characteristics, we found consistent sex differences in the likelihood of referral to the chronic pain clinic, but mixed evidence on differences according to race, and no evidence for differences according to SES. These results provide initial evidence on patient characteristics that increase or limit the likelihood of chronic pain clinic referral. Critical evaluation of pain clinic referral rates and barriers to referral can inform local QI initiatives that aim to increase the referral rate for eligible patients, and thereby improve quality of life and reduce the duration of symptoms among adolescents with chronic pain.
The authors thank Rajesh Ganta, MS (Research Institute, Nationwide Children's Hospital) for assistance with data acquisition for this study.
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