Impact of Out-of-Pocket Expenditure on Physical Therapy Utilization for Nonspecific Low Back Pain: Secondary Analysis of the Medical Expenditure Panel Survey Data

Visits per Episode of Care

This study's estimated value of 5.1 visits per episode of care corresponds with values of 5 to 12.3 determined by other investigators examining physical therapy utilization for low back pain.^1,31,33,54 We found visits per episode of care to vary based on out-of-pocket expenditure. This finding has not been reported previously and has implications for health care policy related to appropriate use of high-value physical therapy.

Predictor Variables

The findings demonstrate that out-of-pocket payment and PCS-12 score negatively predict physical therapy visits per episode of care (P<.001 and P=.002, respectively). Independent of out-of-pocket expenses, type of insurance also was related to number of visits. Privately insured and Medicare-insured people were more likely to have more visits relative to those publicly insured/uninsured (P=.04).

Swinkels et al³³ used multilevel regression analysis to identify predictors of visits per episode of care at the patient, therapist, and practice levels. They identified private health insurance as a significant negative predictor of physical therapy visits per episode of care compared with public health insurance. This finding appears to contradict our finding. During data collection, public insurance was regulated nationally in the Netherlands, reimbursing 9 physical therapy sessions per episode of care.³³ The people included in our category “age 18–64 years with public coverage only for all of the year or uninsured all of the year” either had no insurance or had public coverage regulated at the state level with variable coverage and reimbursement rates that were likely less generous than private insurance. Interestingly, the authors' calculated mean number of visits per episode of care was similar to the number of visits per episode that were reimbursed by public health insurance in the Netherlands and beyond which required private health insurance or out-of-pocket expenditure.³³ This outcome supports our finding that out-of-pocket expenditure predicts physical therapy utilization for adults with nonspecific low back pain.

Other significant factors identified by Swinkels et al³³ were at the patient level (age, sex, chronicity, previous physical therapy, and referral by specialist) and therapist level (age, hours worked per week, content of therapy session, and training). The present study did not have access to therapist-level factors, nor to all patient-level factors that were collected by these researchers. These researchers did not collect information about the patient's severity of presentation, race/ethnicity, or out-of-pocket expense.³³

Jette et al¹ identified predictors of episode intensity, not visits per episode of care. They defined intensity as the total number of visits divided by the number of weeks in the episode of care and found 2 factors that significantly predicted intensity of care: duration since onset of symptoms and region. We did not have access to duration of symptoms and did not find region to predict significantly the number of visits per episode of care.

Our model explained 7.9% (P≤.001) of the variance. This R² value for the final regression equation is similar to those of previous researchers analyzing similar relationships.^1,33,55 Jette et al¹ examined factors determining intensity per episode of physical therapy care for people with low back pain with an equation that explained 11% of the total variance. Swinkels et al³³ identified factors that determine number of physical therapy visits per episode of care with an equation that explained 13% of the variance. Dunlop et al,⁵⁵ describing factors related to one or more visits to a specialty medical physician, constructed equations that explained approximately 12% of the variance. Regression models that include out-of-pocket expenditure with environment-level, therapist-level, and other patient-level factors would be expected to explain a greater proportion of the variance in visits per episode of care.

Health Services Utilization and Physical Therapy

This study demonstrates that out-of-pocket expenditure and PCS-12 score predict visits per episode of physical therapy care. Episodes of care with more than 6 visits were associated with a lower initial PCS-12 score than episodes of care with fewer visits. This finding is important for payers to consider as they design policies to encourage appropriate use of physical therapy by patients with nonspecific low back pain.

We calculated the out-of-pocket expenditure associated with one less visit for patients at the mean number of visits (5.1), after controlling for health-related quality of life, age, and insurance. To do this, we back transformed the log-transformed cost and visits variables that were utilized in the regression models and used the following formula to estimate: natural log (at physical therapy visits per episode + 1/at physical therapy visits per episode) = 0.122 × natural log (cost at one visit increase/cost at visit). The model shows that compared with a patient with OOP expenses of $26.78 and 5 visits, a patient with OOP expenses of $49.09 per visit would have one less visit, and a patient with OOP expenses of $73.15 would have 2 fewer visits. This is due to the logarithmic nature of the equation and the variability of deductibles across the population. These costs illustrate the disincentives that patients face when considering physical therapy if enrolled in high-deductible health insurance plans with high co-payments and coinsurance rates.

Physical therapy reduces pain and improves functional outcomes for people with low back pain,^24–29 and recent evidence demonstrates that early physical therapy for adults with low back pain results in decreased subsequent use of health care services and decreased costs compared with delayed physical therapy.^30–32 Adults with private health insurance who received early physical therapy for low back pain compared with delayed physical therapy had substantially reduced utilization of advanced imaging; additional physician visits, lumbar spine surgery, and lumbar spine injections for 18 months following their initial physician visit³¹; and approximately $4,000 in total health care savings.³¹ Out-of-pocket payments that are too high may result in delayed or reduced access to physical therapy, leading to decreased health-related quality of life and increased downstream costs related to utilization of medical interventions and chronicity.

Physical therapists, as well as other clinicians and professionals who refer patients for physical therapy, must be aware that patients are sensitive to out-of-pocket expenditures. Clinicians must educate each patient about the value of physical therapist services in terms of present and future outcomes, including future use and costs of medical services. Physical therapists must similarly educate referral sources, payers, and legislators at the grassroots and professional association levels so that each understands patients' sensitivity to out-of-pocket expenditures and their role in crafting effective public health policies that will encourage appropriate use of physical therapy while limiting excessive utilization of medical services. Physical therapists must participate in health policy development at local and national levels so that meaningful policies can be developed that ensure access to high-value physical therapy.

The next steps in clinical- and population-based physical therapy research should include identifying all important predictors of physical therapy utilization that may occur at the patient, therapist, clinic, and environment levels; identifying mediating variables for out-of-pocket expenditure that may occur at the patient, therapist, clinic, and environment levels, such as condition severity, type of insurance, annual income, therapist postgraduate training, proportion of treatment time spent with direct supervision of the therapist, and geographical area; and identifying out-of-pocket expenditure “tipping points” that prohibit appropriate use of physical therapy. As data collection becomes more comprehensive at the clinical and national levels, such efforts will be more feasible.

Limitations

There are several limitations to this study. We utilized a nonexperimental design, so causal inferences may not be drawn. The study design lacked information about the patients' presentation to therapy, including severity of symptoms. Severity of symptoms likely influences the number of visits per episode of care.⁵⁶ The study design also lacked information about the therapist, clinic environment, content of physical therapy care delivered, and timing of therapy delivery. Care that is adherent to evidence-based low back pain guidelines is likely to yield better outcomes.⁵⁷ Early therapy is associated with better outcomes for people with low back pain.^30–32 Our calculated expenditures may be conservative, as MEPS has been shown to underestimate health care expenditures.^47–49 The PCS-12 and MCS-12 scores were not taken coincidental with the start of the physical therapy episode of care, so they may not reflect the actual health-related quality of life at the time care was delivered. The data files indicated whether physical therapy was provided but not by whom it was provided (eg, physical therapist or other provider), which may affect volume and quality of services. Additionally, more than one medical condition may be treated during a visit, so all costs may not be specific for low back pain. Missing visit dates were replaced by the 15th day of the month. As a new physical therapy episode of care began if more than 30 days elapsed between consecutive visits, this change should not significantly affect the mean total visits per episode of care. The study population comprised patients with nonspecific low back pain, so the results may not apply to patients receiving physical therapy with other health conditions.

In conclusion, health services utilization research is lacking in the US physical therapy literature, and there is a dearth of research examining the effect of out-of-pocket payment on physical therapy use. However, co-payments for physical therapy in the United States are reported to be as high as $50 to $100 per visit.^58,59

This study identified out-of-pocket expenditure as a predictor of physical therapy visits per episode of care. This finding is critical for public health policy makers and payers to investigate and consider as they design policies to encourage appropriate use of high-value physical therapy because out-of-pocket payments that are too high may result in reduced access to physical therapy by patients with nonspecific low back pain; reduced health-related quality of life; and increased downstream costs related to utilization of medical interventions, chronicity, and disability.

Future physical therapy health services utilization research efforts should include identifying all variables that influence physical therapy utilization; identifying mediating variables for out-of-pocket expenditure that may occur at the patient, therapist, and clinic levels; and identifying out-of-pocket expenditure “tipping points” that prohibit appropriate use of physical therapy, particularly for people whose deductibles represent a large proportion of their annual income.

In addition to building a base of health services utilization research in physical therapy, it is essential that more physical therapists participate in public health and health care policy development at the local, state, and national levels. This participation is necessary to eliminate the silos in which health care providers reside and promote collaborative health care teams that maximize patient outcomes through effective communication and use of high-value care.