Table 3

Initial HCP Primary Study Characteristics^{^a}

Study	Country	No. and Source of Participants	Setting	Research Aims	Nonmedical Provider Type	Comparator	Definition of Episode of Care	Duration	Outcomes Relating to Health Care Utilization	Secondary Outcomes Measured
Carey et al²³ (1995)	United States	1555 consecutively selected patients; 208 randomly selected PCPs (87 PCPs, 64 chiropractors, 29 orthopedic surgeons, 28 health maintenance organization providers)	Primary care	To determine whether outcomes and charges vary according to the type of provider initially seen for an episode of acute LBP	Chiropractor	PCP, orthopedic surgeon	No LBP in 2 mo preceding current episode; people who had not previously seen HCP for current episode	6 mo from initial visit	Medication prescription, radiography, advanced imaging, cost of care, hospitalization, frequency of visits	Function measured by Adapted Sickness Impact Profile; patient satisfaction with care

Sundararajan et al³³ (1998)	United States	1580; secondary analyses of data from Carey et al²³ (1995)	Primary care	To describe patterns of provider use associated with an acute episode of nonspecific LBP and their impact on cost	Chiropractor	PCP, orthopedic surgeon	No LBP in 2 mo preceding current episode; people who had not previously seen HCP for current episode	6 mo from initial visit	Seeking care from multiple providers and cost of care	None

Liliedahl et al²⁹ (2010)	United States	85,402; Blue Cross Blue Shield of Tennessee claims database of fully insured patients (unrestricted access to primary and specialty providers); October 1, 2004–September 30, 2006	Primary care, ED	To determine whether there are differences in the cost of LBP care when a patient is able to choose a course of treatment with a medical doctor vs a doctor of chiropractic	Chiropractor	PCP (including osteopaths)	All reimbursed care delivered between first and last encounters with HCP for LBP; clean period of 60 d of no HCP use prior to current episode	Unspecified	Cost of care	None

Henschke et al²⁸ (2013)	Australia	1328; secondary analyses of cohort study with consecutive patient selection	Primary care	To determine predictors of satisfaction with care and symptoms in patients with acute LBP 1 y after presentation to primary care	Physical therapist, chiropractor	PCP	No experience of an episode of back pain in month prior to presentation	12 mo after index visit	None	Satisfaction with care

Fritz et al²⁴ (2015)	United States	2289; University of Utah Healthy U Medicaid managed health plan database; January 1, 2012–December 30, 2012	Primary care, ED	To examine physical therapy utilization by Medicaid enrollees with new LBP consultations and to evaluate associations with future health care utilization and LBP-related costs	Physical therapist	PCP and ED entry	No LBP-related claims in preceding 90 d	12 mo from initial visit	Radiography, advanced imaging, ED visits, epidural injections, surgery, cost of care	None

Fritz et al²⁵ (2016)	United States	747; University of Utah database enrollees with private employer–based coverage; January 1, 2012–January 31, 2013	Primary care and secondary care	To explore associations between entry settings and future LBP-related utilization and costs	Physical therapist, chiropractor	PCP	New consultation for LBP in which no charges associated with LBP received in 90 d prior to entry visit	12 mo from initial visit	Radiography, advanced imaging, ED care, epidural injections, surgeon visit, surgery, cost of care	None

Frogner et al³⁰ (2018)	United States	148,866; Healthcare Cost Institute claims database of patients with private insurance; 2009–2013	Primary care, secondary care, ED	To compare differences in opioid prescription, health care utilization, and costs among patients who had LBP and who saw a physical therapist at the first point of care, at any time during the episode, or not at all	Physical therapist	Delayed physical therapy or no physical therapy (including a mix of chiropractors, orthopedists, and acupuncturists)	Patients with new LBP diagnosis from “index date” that followed 6-mo clean period in which no visits for LBP	12 mo from initial visit	Opioid prescription, radiography, advanced imaging, ED care, hospitalization, costs	None

Azad et al³¹ (2019)	United States	478,981; Truven Health MarketScan Commercial claims and Encounters database (primarily comprising patients with private insurance); June 1, 2009–December 31, 2011	Primary care, secondary care, ED	To determine whether provider specialty influences patterns of opioid use long after the initial diagnosis	Physical therapist, chiropractor, nurse practitioner, acupuncturist, physician assistant	PCP	Defined as first visit at which enrollee had claim with ICD-9 code that met criteria of LBP or lower extremity radicular pain, without any of these codes in 12 mo prior to presentation	12 mo from initial visit	Opioid prescription	None

Kazis et al²⁷ (2019)	United States	216,504; OptumLabs Data Warehouse. Database of commercial and Medicare Advantage enrollees; 2008–2013	Primary care, secondary care, ED	To examine the association of initial provider treatment with early and long-term opioid use in a national sample of patients with new-onset LBP	Physical therapist, chiropractor, acupuncturist	PCP	New-onset LBP defined as no diagnosis of LBP or back procedures, including spinal surgery, spinal injections, and spinal nerve stimulators, during 12-mo period prior to index event	12 mo from initial visit	Opioid prescription	None

O’Reilly-Jacob et al³² (2019)	United States	45,295; Medicare claims database from 18 Dartmouth Atlas of Healthcare hospital referral regions; 2012–2013	Primary care	To compare the rates of low-value back images ordered by primary care physicians and primary care nurse practitioners after primary care visits for first-time back pain	Nurse practitioner	PCP	Patients without recent history of back pain or back pain–related hospitalizations	30 d from initial visit	Radiography, advanced imaging	None

Garrity et al²⁶ (2020)	United States	60,598; OptumLabs Data Warehouse. Database of commercial and Medicare Advantage enrollees; 2008–2013	Primary care	To evaluate the association of level of access to physical therapist services with LBP-related health care utilization and costs	Physical therapist (in restricted- and unrestricted- access states)	PCP	New-onset LBP defined as primary LBP claim and no prior claims with diagnosis of LBP or prior back procedures, including spinal surgery, spinal injections, and spinal nerve stimulators, during 12-mo period prior to index event	90 d from initial visit	Cost of care (physical therapist vs PCP); physician visits, radiography, advanced imaging, and back procedures analyzed between access levels only	None

^aED = emergency department; HCP = health care provider; ICD-9 = International Classification of Diseases, Ninth Revision; LBP = low back pain; PCP = primary care physician.