Cost-effectiveness Of Treatments for Low Back Pain
Low back pain (LBP) is a common, costly, and recurrent problem in the United States. There are three main classes of LBP: spinal stenosis, disc displacement or herniation, and idiopathic (non-specific), with the last class comprising 85% of the cases.1 The lifetime risk of LBP is estimated at 85% in the United States.2 A recent Medical Expenditure Panel Survey (MEPS) of adults showed that more than a quarter reported LBP within the previous 3 months.3 Recurrences are common: The one-year recurrence rates have been estimated at between 20% and 44%. The emerging picture is that of a chronic condition with acute exacerbations.1,2
In most patients, pain resolves within a few weeks or months regardless of the etiology or treatment, but in about 8% of cases, pain lasts at least 3 months. About 5% of patients have unremitting pain at 22 months.4
The burden to the healthcare system is considerable. LBP is the second-leading symptomatic cause for physician visits, the third-most-common reason for surgical procedures, and the fifth-most-common reason for hospitalizations.2 In 2005, age- and gender-adjusted expenditures among those with LBP was $2580 (73%) higher than among people without LBP.3
Many treatments are available for LBP, including physical and chiropractic therapy, several classes of pharmaceuticals, electrotherapy, surgery, and others. Healthcare spending on imaging and treatments increased by 65% between 1997 and 2005, but notably there was no concomitant increase in patients’ health or functional status.3
We performed a cost-effectiveness analysis of treatments for episodes of idiopathic LBP and LBP caused by disc herniation using managed-care claims data. The therapies included those commonly used with patients whose pain is refractory to rest and over-the-counter (OTC) drug therapy: physical therapy, occupational therapy, chiropractic care, transcutaneous electrical nerve stimulation (TENS), and opiates. We defined “cost” from the payer’s perspective (eg, reimbursements) and effectiveness as the length of the LBP episode. The costs and episode lengths associated with these three treatments were compared separately in the two diagnostic indications.
How the Study Was Performed
The perspective of this cost-effectiveness analysis (CEA) was the payer. We used 2005 managed-care claims data from a commercial vendor allied with a major healthcare system that encompasses health plans across the United States. Inpatient, outpatient, physician, and pharmacy claims were included. Following a clean period, members with the diagnoses of LBP in the following diagnostic groups were included: displaced or herniated disc (inter-vertebral disc disorders, disc degeneration, and sciatica) and idiopathic/non-specific LBP (backache, lumbago, non-allopathic lesions, strains, and sprains). Episodes were assigned to idiopathic LBP if they contained appropriate International Classification of Disease, 9th Revision (ICD-9) codes and contained no ICD-9 codes for herniated disc. Members with concurrent diagnoses of cancer, trauma, intravenous (IV) drug use, or neurological impairment were excluded.
Claims-based episode definitions are not consistent in the literature, so we constructed our own definition using previous work as a starting point.5-10 We adjusted our definition to eliminate any correlation between the number of episodes experienced by a member and the length of episodes. An episode of LBP was defined as the time from the date of the first claim with a relevant primary or secondary diagnosis to the date of the last claim with either: (1) a relevant diagnosis if the claim was for inpatient, outpatient, or physician services, or (2) a relevant National Drug Code (NDC) if the claim was for pharmaceuticals, in which case days’ supply was added to the service date to obtain the end-of-episode date. A clean period had to follow the end-of-episode date; the length of the clean period depended on the type of claim (see Table 1). Episodes with a single claim were considered to have an episode length of 0 days. Episodes with length of 0 days were distributed evenly throughout the year and were not an artifact of the use of a single year of data. (We dealt with this problem in the statistical analysis below.)
Effectiveness was defined as the length in days of the episode. (We assumed that the pain was essentially resolved when the member did not seek further treatment.) Because claims from a single calendar year were included, only episodes with an adequate clean period (indicating that the episode had ended) were included. To eliminate bias in the estimate of the length of episodes due to this requirement, we adjusted for the start date of the episode (relative to January 1, 2005) in the analysis.
For the therapy analysis, therapies during the episodes were identified by Current Procedural Terminology (CPT) codes and assigned to the following treatment groups (episodes could include treatments in more than one group): (1) Outpatient (OUT); (2) TENS/electro-acupuncture (TENS); (3) PT/Osteopathic/chiropractic (PT); (4) Opioids (OPI); and (5) NSAIDs [non-steroidal anti-inflammatory drugs] (NS). Because NSAID claims were so rare, we concluded that most NSAIDs for LBP were non-prescription uses and likely to be common to most episodes of LBP. Episodes with only treatments 1 and/or 5 were eliminated from the analysis; those with 1 and/or 5 combined with 2 and/or 3 and/or 4 were included and analyzed according to the combination of treatments 2, 3, and 4.
The claims data set included allowed charges but not reimbursed amounts (which are payer costs). Therefore, costs per episode were estimated for hospitalizations and physician services with any of the previously listed primary or secondary diagnoses from the Medicare 2007 national average diagnosis-related group (DRG) and CPT reimbursements (based on relative value units [RVUs] or relative weights [RWs] and the 2007 unit payments). Outpatient (OP) hospital services in these commercial claims data contained no CPT codes, so it was not possible to assign an Ambulatory Patient Classification (APC)–based reimbursement to these services. Instead, we applied the Medicare 2007 outpatient cost-to-charge ratio (CCR) to the allowed charges on each OP visit. Drug costs were estimated from the pharmacy claims by first estimating the regression of allowed charges on paid charges in a small sample (n=400) of drugs used to treat LBP in which both allowed and paid charges were provided, and then using the conversion equation to estimate paid amounts from allowed charges in the full data set.