measurement properties of the functional rating index

SPINE Volume 43, Number 22, pp E1340–E1349

� 2018 Wolters Kluwer Health, Inc. All rights reserved.

LITERATURE REVIEW

Measurement Properties of the FunctionalRating Index

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A Systematic Review and Meta-analysis

Zhongfei Bai, MSc,� Tian Shu, BSc,� Jiani Lu, MSc,� and Wenxin Niu, PhD�,y

findings show strong positive evidence for structural validity and
Study Design. A systematic review and meta-analysis.Objective. To assess the measurement properties of the Func-
tional Rating Index (FRI) and determine whether its measurement

properties are comparable with other region-specific question-

naires.Summary of Background Data. In addition to low back pain

(LBP) and neck pain (NP), multiregion spinal pain (SP) is a

common problem with a considerable prevalence in the general

population. The FRI was built to assess physical functioning in

patients with SP. However, a systematic review assessing

evidence of its measurement properties in separated populations

and a comparison with other questionnaires regarding each

measurement property is lacking.Methods. Articles concerning the FRI’s measurement properties

or head-to-head comparison with other questionnaires on

measurement properties were obtained from MEDLINE, Embase,

CINAHL, and PsycINFO. Two reviewers independently reviewed

the articles, extracted data, and conducted the methodological

quality assessment. The COnsensus-based Standards for the

selection of health Measurement INstruments (COSMIN) check-

list was used to assess the methodological quality of the

included studies.Results. A total of 18 studies evaluating the FRI’s measurement

properties, including seven that carried out head-to-head com-

parisons in at least one measurement property with other

questionnaires, were included in the current review. Our

the �Occupational Therapy Department, Shanghai YangZhi Rehabili-Hospital (Shanghai Sunshine Rehabilitation Center), Tongji Univer-chool of Medicine, Shanghai, China; and yDepartment ofilitation Sciences, Tongji University School of Medicine, Shanghai,.

wledgment date: September 14, 2017. First revision date: March 15,Second revision date: April 4, 2018. Acceptance date: April 5, 2018.

anuscript submitted does not contain information about medical(s)/drug(s).

e & Technology Project Foundation of Shanghai Sports Bureau (No.7) funds were received in support of this work.

levant financial activities outside the submitted work.

ss correspondence and reprint requests to Wenxin Niu, PhD, Depart-f Rehabilitation Sciences, Tongji University School of Medicine, No.

Siping Rd, Shanghai, 200092 China; E-mail: [email protected]

10.1097/BRS.0000000000002690

www.spinejournal.com

right © 2018 Wolters Kluwer Health, Inc. Unau

internal consistency in patients with SP and LBP. Evidence for

most of the FRI’s measurement properties is limited, conflicting,

or even unknown. The current evidence shows that the FRI is

comparable with both the Oswestry Disability Index and the

Neck Disability Index in responsiveness. However, relevant

information about the majority of the other measurement

properties is lacking.Conclusion. Our finding suggests that clinicians and research-

ers should use the FRI with caution until there are more studies

with high methodological quality that support the view that it is

positive in all measurement properties, especially in regard to

patients with multiregion SP.Key words: functional rating index, head-to-head comparison,low back pain, measurement properties, meta-analysis, neckpain, reliability, review, spinal pain, validity.Level of Evidence: 1Spine 2018;43:E1340–E1349

Spinal pain (SP), a common complaint with a highlifetime prevalence,1,2 can be subdivided into neckpain (NP), upper back pain, low back pain (LBP), and

multiregion pain. LBP and NP, in particular, are commonconditions, with a considerable number of reports ofpatients with NP and concurrent LBP in various popula-tions.3–7 SP has a great number of negative effects onpatients’ physical functioning, daily activities, social life,and work,1,8 and a major impact on the healthcare systemhas also been observed.9

To measure the severity of limitation in physical func-tioning and detect effectiveness of treatments, numerousregion-specific patient-reported outcome (PRO) question-naires like the Oswestry Disability Index (ODI), Roland-Morris Disability Questionnaire (RMDQ), and Neck Dis-ability Index (NDI), which are indicators of patients’ per-ceived level of disability, have been developed and widelyused.10–12 Despite these questionnaires’ good measurementproperties and relatively simple application for patients andhealthcare providers, they have limitations in situationswhere pain is multiregional rather than localized. This ismainly because they have been developed for pain in a single

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thorized reproduction of this article is prohibited.

mailto:niu@tongji�.�edu.cn

LITERATURE REVIEW Measurement Properties of the Functional Rating Index � Bai et al

C

region, and the relationship between items and constructsmay change if used in multiregion spinal pain patients.13

Therefore, we cannot directly choose only one from amongthe ODI, RMDQ, and NDI to measure physical functioningof patients with multiregion pain.

In order to reduce the time spent on completion, scoring,and analysis, Feise and Michael-Menke14 developed a ques-tionnaire, the Functional Rating Index (FRI), for patientswith SP. According to the developers’ original objective, theFRI could be used in patients with pain in the spine,including any single-region pain (e.g., NP or LBP), andmultiregion pain. They found that the test-retest reliabilitywas excellent and that the FRI correlated strongly with the12-item short-form health survey (physical componentscore) in the entire population of patients with SP includingthose with cervical, thoracic, and lumbar pain.14 In addi-tion, the clinical utility was convenient and timesaving.However, as factor analysis was not performed, the FRI’sstructural validity—the degree to which the scores of aquestionnaire are an adequate reflection of the dimension-ality of the construct to be measured—could not be ascer-tained.15 Internal consistency can be calculated when thoseitems are from one dimensionality.16 Although the devel-opers assumed that all selected items from the ODI and NDIpool could measure NP and LBP, exploratory factor analysiswas still required to verify it. Afterward, numerous FRIvalidation studies were carried out, but the findings wereinconsistent. For example, while several studies found excel-lent test-retest reliability,17,18 one study reported moderatetest-retest reliability.19 Thus, if the FRI’s measurementproperties are comparable with other region-specific ques-tionnaires, it will be another advantage for alternative use.To verify the above hypothesis, a systematic review includ-ing studies conducting head-to-head comparison with otherregion-specific questionnaires is required to avoid any biasesresulting from population, design, and clinical setting.

The FRI developers summarized that it had favorablemeasurement properties based on ten independent studies.20

While nine of these performed statistical analysis based onpatients with single-region pain, the developers performedstatistical analysis based on the entire SP population includ-ing those with cervical, thoracic, and lumbar pain. Further-more, in the developers’ review,20 comprehensivemethodological quality evaluation for the included studiesand evidence synthesis were lacking. In another descriptivereview,21 across various studies, the FRI was found to haveoverall positive measurement properties. However, evidencesynthesis in patients with NP, LBP, and SP was lacking.

Up to this day, there have been studies evaluating theFRI’s measurement properties in patients with NP and LBP.Meanwhile, some researchers have calculated the FRI’smeasurement properties based on the entire SP population,rather than any region-specific population. Therefore, theaims of this systematic review are to summarize whether theFRI’s measurement properties are good enough to supportits clinical application in SP, LBP, and NP and to determinewhether its measurement properties are comparable with

Spine

opyright © 2018 Wolters Kluwer Health, Inc. Unau

other region-specific questionnaires like ODI, RMDQ,and NDI.

MATERIALS AND METHODS

Data Sources and SearchA computerized literature search was conducted in thefollowing databases: MEDLINE, Embase, CINAHL, andPsycINFO. In each database, the search was conductedusing the keyword ‘‘functional rating index.’’ As the FRIwas introduced in 2001, the publication date limit wasestablished at 2000. Reference lists of previous systematicreviews were also screened.20,21 Google Scholar was alsosearched using the above keyword. The last search was onAugust 1, 2017.

Study SelectionStudies were included if they met the following criteria: (1)peer-reviewed journal articles published in English; (2) eval-uating at least one measurement property of the FRI. Studieswere excluded if (1) their full texts were not available; (2) theFRI was only involved as a comparator or criterion forhypothesis testing to assess other questionnaires’ measure-ment properties; (3) essential statistical results such as samplesize and specific parameters related to the FRI’s measurementproperties were missing. First, two reviewers (Z.B. and T.S.)independently selected all records based on the titles andabstracts. Secondly, full texts were downloaded. Then, thetwo reviewers had a face-to-face discussion to reach anagreement on study inclusion, and any discrepancies wereresolved by a third reviewer (W.N.).

Data Extraction and Quality AssessmentA customized form involving measurement properties waspre-produced for data extraction with regard to the includedstudies’ general characteristics. For measurement proper-ties, we extracted not only results of statistical analysis butalso details of each study in terms of sample size, statisticalmethod, time interval for test-retest reliability, and mea-surement error, among other things. The COnsensus-basedStandards for the selection of health Measurement INstru-ments (COSMIN) checklist, which aims for evidence-basedinstrument selection, was used to evaluate the methodologi-cal quality of original studies.15,16,22,23

Data SynthesisEvaluations of the FRI’s measurement properties were basedon homogeneous studies on populations and methodologicalquality. Meta-analyses of internal consistency (Cronbach’salpha), test-retest reliability (intraclass correlation coeffi-cient, ICC), and hypotheses testing (Pearson’s correlationcoefficient) were carried out in Comprehensive Meta-Analy-sis 2.2 software (Englewood, NJ) if there were more thanthree homologous studies in existence. This software canautomatically convert the correlation coefficient to Fisher’sz value which is necessary for meta-analysis.24 The meta-analyses were conducted using the random effect (RE) model

www.spinejournal.com E1341



because all values of I2 were above 50%.25 The remainingmeasurement properties were qualitatively synthesized.

Measurement properties for the FRI are considered ‘‘pos-itive,’’ ‘‘indeterminate,’’ or ‘‘negative’’ according to thecriteria laid down by Terwee et al. (see Supplemental DigitalContent, Table 1, http://links.lww.com/BRS/B353).26 Amodification in another systematic review was alsoadopted,27 that is, the measurement error is acceptableand is considered positive if the smallest detectable change(SDC) is smaller than 20% of the total score. Furthermore,as the interpretation of limits of agreement (LoA) can besimilar to the SDC, we added one more criterion that apositive rating is given if both the upper and lower limits ofagreement are smaller than 20% of the total score. If SDC isnot calculated in the included studies but standard measure-ment error (SEM) is available, it is calculated as follows26:

SDC ¼ 1:96�ffiffiffi

2p� SEM:

The levels of evidence approach proposed by the CochraneBack Review Group was used for the FRI’s final measurementproperty evaluation (see Supplemental Digital Content,Table 2, http://links.lww.com/BRS/B353).12,21,27–29 Theevidence was considered strong if there were consistent find-ings in multiple studies of good methodological quality or inone study of excellent methodological quality. The evidencewas moderate if there were consistent findings in multiplestudies of fair methodological quality or in one study of goodmethodological quality. The evidence was limited in the case

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E1342 www.spinejournal.com

Copyright © 2018 Wolters Kluwer Health, Inc. Unau

of only one study of fair methodological quality and conflict-ing if there existed conflicting findings. The evidence wasgraded as unknown if there were only studies of poor meth-odological quality. The level of evidence for each of the FRI’smeasurement properties in SP, LBP, and NP are separatelyreported. For head-to-head comparison with other region-specific questionnaires, the level of evidence approach wasused again.

RESULTSA total of 18 studies were eligible14,17–19,30–43; the flow-chart of the selection is presented in Figure 1. The character-istics of each included study are presented in Table 1. Allincluded studies evaluated at least one measurement prop-erty of the FRI, and seven studies also carried out head-to-head comparisons with other measurement tools. In addi-tion to this, two studies carried out analyses based onpatients with SP.14,43 The other studies performed statisticalanalysis based on separated population, LBP or NP, and didnot find studies that performed statistical analysis based onpatients with multiregion pain. Another two studiesrecruited patients with whiplash-associated disorders whichwe considered one type of NP.35,42 The methodologicalquality of these studies is presented in Table 2.

Structural ValidityFour excellent-quality studies assessed the FRI’s struc-tural validity. Their results showed that the FRI was unidi-mensional in SP43 and LBP.39 Nevertheless, two studies

xcluded 850)

es excluded, asons 13) other nt tools alidation

ews

Figure 1. Flowchart of results of search strategy andselection of articles.

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http://links.lww.com/BRS/B353

http://links.lww.com/BRS/B353

TABLE 1. Characteristics of the Included Studies

StudyCountry

(Language) Design Setting PopulationSample

SizeMeasurementProsperities

Head-to-HeadComparator

Feise and Michael-Menke14

USA (English) Prospective cohort Chiropractic clinics SP 139 Internal consistency; test-retestreliability; hypothesis-testing;responsiveness

Gabel et al.43 Australia (English) Prospective cohort Physical therapyoutpatient clinics

SP 173 Structure validity; internalconsistency; test-retestreliability; measurement error;responsiveness

Chansirinukor38 Thailand (Thai) Prospective cohort Physical therapydepartment

LBP and NP LBP: 161;NP: 84

Internal consistency; test-retestreliability; hypothesis-testing;measurement error; cross-cultural validity

Bayar et al.30 Turkey (Turkish) Prospective cohort Aging center LBP 37 Internal consistency; test-retestreliability; hypothesis-testing

Chansirinukor etal.31

Australia (English) Retrospectivecohort

Physical therapy clinic LBP 143 Test-retest reliability;measurement error;responsiveness

RMDQ-18

Ceran and Ozcan32 Turkey (Turkish) Prospective cohort Rehabilitationdepartment

LBP 84 Internal consistency; test-retestreliability; hypothesis-testing;cross-cultural validity

Costa et al.34 Brazil (Brazilian-Portuguese)

Prospective cohort Physiotherapy clinics LBP 140 Internal consistency; test-retestreliability; hypothesis-testing;cross-cultural validity;responsiveness

RMDQ-24

Ansari et al.17 Iran (Persian) Cross-sectional Public physiotherapyclinics

LBP LBP: 100;Healthy: 50

Internal consistency; test-retestreliability; hypothesis-testing;cross-cultural validity

Wei et al.18 China (SimplifiedChinese)

Cross-sectional Outpatient departmentof orthopedics

LBP 115 Internal consistency; test-retestreliability hypothesis-testing;cross-cultural validity

ODI

Naghdi et al.39 Iran (Persian) Cross-sectional Sport clubs LBP LBP: 100;Healthy: 50

Internal consistency; test-retestreliability; measurement error;structural validity; hypothesis-testing

Childs and Piva19 USA (English) Multicenter RCT Clinics in varioushealthcare settings

LBP 131 Test-retest reliability;measurement error;hypothesis-testing;responsiveness

ODI

Costa et al.36 Brazil (Brazilian-Portuguese)

Prospective cohort Physiotherapy clinics LBP 99 Internal consistency; test-retestreliability; hypothesis-testing;responsiveness

RMDQ-24

Ansari et al.37 Iran (Persian) Cross-sectional Physiotherapy clinics NP NP: 100;Healthy: 50

Internal consistency; test-retestreliability; structural validity;hypothesis-testing

Wei et al.40 China (SimplifiedChinese)

Cross-sectional Department ofOrthopedics

NP 122 Internal consistency; test-retestreliability; hypothesis-testing

Naghdi et al.41 Iran (Persian) Cross-sectional Sport clubs NP NP: 100;Healthy:50

Internal consistency; test-retestreliability; measurement error;structural validity; hypothesis-testing

Lee et al.33 Korea (Korean) Prospective cohort Physiotherapydepartments

NP NP: 180;Healthy: 81

Internal consistency; test-retestreliability; cross-culturalvalidity; responsiveness

NDI

Stewart et al.35 Australia (English) RCT Insurance claimsdatabase

WAD 132 Responsiveness NDI

Rebbeck et al.42 Australia (English) One cohort studyand two RCT

Physiotherapy clinicsand Insuranceclaims database

WAD 99 Internal consistency;responsivenessWAD 250

WAD 132

LBP indicates low back pain; NDI, Neck Disability Index; NP, neck pain; ODI, Oswestry Disability Index; RCT, randomized control trial; RMDQ, Roland-Morris Disability Questionnaires; SP, spinal pain; WAD, whiplash associated disorder.


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reported conflicting results on whether the FRI had one ortwo latent factors in NP.37,41 Ansari et al.37 conductedsubsequent factor analysis and revealed that the remainingitems were unidimensional when ‘‘standing’’ and ‘‘walking’’were discarded.

Internal ConsistencyA poor-quality study and an excellent-quality study showedCronbach’s alpha of 0.92 and 0.908 respectively in patients

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with SP.14,43 One excellent-quality study showed that theFRI had a positive internal consistency in LBP (Cronbach’salpha¼0.90).39 For the FRI’s internal consistency inpatients with NP, two excellent-quality studies reportedinconsistent findings due to conflicting results on structuralvalidity.37,41 Another seven and three studies respectivelyalso reported Cronbach’s alpha of the FRI inLBP17,18,30,32,34,36,38 and NP.33,40,42 However, the qualityof each study was poor.



TABLE 2. Methodological Quality of Each Included Study per Measurement Properties

Study Population

Structural

Validity

Internal

Consistency

Test-retest

Reliability

Measurement

Error

Content

Validity

Hypotheses

Testing

Cross-cultural

Validity

Responsiveness

MHT ROC

Feise andMichael-Menke14

SP Poor Fair Poor Fair

NP Poor

TP Poor

LBP Poor

Gabel et al.43 SP Excellent Excellent Fair Fair Poor

Chansirinukor38 LBP Poor Poor Poor Fair Poor

NP Poor Poor Poor Fair Poor

Bayar et al.30 LBP Poor Fair Poor

Chansirinukor et al.31 LBP Fair Fair Poor Poor

Ceran and Ozcan32 LBP Poor Fair Poor Poor

Costa et al.34 LBP Poor Fair Fair Poor Poor

Ansari et al.17 LBP Poor Fair Fair Poor

Wei et al.18 LBP Poor Poor Fair Poor

Naghdi et al.39 LBP Excellent Excellent Good Good Fair

Childs and Piva19 LBP Fair Fair Fair Poor Excellent

Costa et al.36 LBP Poor Fair Fair Poor Good

Ansari et al.37 NP Excellent Excellent Fair Fair

Wei et al.40 NP Poor Poor Fair

Naghdi et al.42 NP Excellent Excellent Fair Fair Fair

Lee et al.33 NP Poor Fair Poor Poor Good

Stewart et al.35 WAD Poor Good

Rebbeck et al.42 WAD Poor Poor Good

WAD Poor Poor Good

WAD Poor Poor Good

LBP indicates, low back pain; MHT, method of hypothesis testing; NP, neck pain; ROC, Receiver Operator Curve; SP, spinal pain; TP, thoracic pain; WAD,whiplash associated disorder.


Test-Retest ReliabilityTwo fair-quality studies assessing test-retest reliability indi-cated that the FRI was positive (ICC¼0.99, 0.948) inSP.14,43 In LBP, all studies rated as good quality(ICC¼0.97),39 fair quality (ICC¼0.859; 95% CI¼0.745to 0.924; I2¼92.78%; RE) (Figure 2),17,19,30–32,34,36 orpoor quality (ICC¼0.82, 0.948)18,38 showed that the FRIhad positive test-retest reliability. In NP, meta-analysisbased on fair-quality studies showed that the FRI hadpositive test-retest reliability (ICC¼0.945; 95%CI¼0.868 to 0.978; I2¼86.85%; RE) (Figure 3),33,37,41

and similar results were reported in two poor-quality studies(ICC¼0.89, 0.97).38,40

Measurement ErrorOne fair-quality study supported that the FRI had a positivemeasurement error (SEM¼4.14%; SDC¼9.66%) in SP.43

In LBP, the positive measurement error was supported by agood-quality study (LoA¼ –5.5% to 10.2%)39 and a poor-quality study (SEM¼0.9%; SDC¼2.3%)38 while conflict-ing results were reported in two fair-quality studies(SDC¼24.4%, 20.8%).19,31 It is notable that one studycarried out test-retest reliability in patients whose workstatus did not change rather than in patients with stablephysical functioning.31 A fair-quality study assessing mea-surement error in NP showed a positive result.41



Content ValidityThe developers clearly stated that the FRI was designed tomeasure subjective perception of functioning in patientswith spinal musculoskeletal problems, especially those withsymptoms in multiple regions.14 The FRI is made up of sixitems from both the ODI and NDI, one item (work) from theNDI, two items (walking and standing) from the ODI, andan additional item (frequency of pain). However, there wereno studies evaluating the FRI’s content validity forany population.

Hypotheses TestingOne poor-quality study reported the Pearson’s correlationcoefficient between the FRI and Disability Rating Index,12-item short-form Physical Component score, and12-item short-form Mental Component score in SP.14 Itshowed that the FRI correlated with LBP patients’ painintensity (r¼0.735; 95% CI¼0.641 to 0.807;I2¼77.77%; RE) (Figure 4),17,18,34,36,39 RMDQ(r¼0.755; 95% CI¼0.670 to 0.821; I2¼76.49%; RE)(Figure 5),17,34,36,38,39 and ODI (r¼0.825; 95%CI¼0.583 to 0.932; I2¼96.6%; RE) (Figure 6)17–19,38

based on fair-quality studies. In NP, high pooled correla-tion coefficients between the FRI, pain intensity(r¼0.866; 95% CI¼0.700 to 0.943; I2¼93.88%; RE)(Figure 7), and ODI (r¼0.900; 95% CI¼0.449 to 0.986;

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Figure 3. Meta-analysis on test-retest coef-ficient in neck pain based on seven fairstudies.

Study name Statistics for each study Correlation and 95% CI

Lower Upper Total Correlation limit limit Z-Value

Lee 2006 40 0.860 0.749 0.924 7.867Ansari 2012 50 0.960 0.930 0.977 13.340Wei 2012 60 0.970 0.950 0.982 15.796

0.945 0.868 0.978 7.623

-1.00 -0.50 0.00 0.50 1.00

Figure 2. Meta-analysis on test-retest coef-ficient in low back pain based on sevenfair studies.



Chansirinukor 2005 96 0.670 0.542 0.767 7.819Bayar 2004 37 0.913 0.836 0.955 9.010Childs 2005 41 0.630 0.400 0.785 4.570Ceran 2006 84 0.926 0.888 0.951 14.666Costa 2007 140 0.950 0.931 0.964 21.440Costa 2008 99 0.860 0.798 0.904 12.672Ansari 2011 50 0.810 0.686 0.888 7.727

0.859 0.745 0.924 7.737

-1.00 -0.50 0.00 0.50 1.00


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I2¼99.00%; RE) (Figure 8) were also found based onfair-quality studies.37,38,40,41

Cross-cultural ValidityThe FRI has been translated into Turkish,32 Korean,33

Brazilian-Portuguese,34 Persian,17 Chinese,18 and Thai.38

All except one study32 described the procedures of transla-tion and cross-cultural adaptation in detail. All studies wererated as poor-quality because neither confirmatory factoranalysis nor Rasch analysis was used to assess whether thetranslated versions had a factor structure consistent with theoriginal English version.

ResponsivenessIn SP, one fair-quality study reported that the FRI’s respon-siveness (SRM¼1.24) was in accordance with a prior

Figure 4. Meta-analysis on correlationcoefficient between Functional RatingIndex and pain intensity in low back pain.

Study name S

Total Correlat

Costa 2007 140 0.Costa 2008 99 0.Ansari 2011 100 0.Wei 2012 115 0.Naghdi 2015 100 0.

0.

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hypothesis (above 0.8).14 In LBP, there were inconsistentresults on the FRI’s responsiveness (AUC¼0.46 vs. 0.93)between a good-quality study and excellent-qualitystudy.19,36 In NP, inconsistency in the FRI’s responsivenesswas also observed among good-quality studies.33,35,42 Otherstudies also adopted hypothesis testing to assess the FRI’sresponsiveness. However, owing to unclear prior hypothe-ses, the resulting quality was poor.

Head-to-Head Comparison With Other PROQuestionnairesThe FRI’s responsiveness was comparable with both the ODI(AUC¼0.93; 95% CI¼0.89 to 0.98)19 and NDI(AUC¼0.79 vs. 0.79; 0.79 vs. 0.76),33,35 supported by anexcellent study and good studies, respectively. In addition,both the FRI and RMDQ moderately correlated with pain

tatistics for each study Correlation and 95% CI

Lower Upper ion limit limit Z-Value

670 0.567 0.752 9.490630 0.494 0.736 7.264750 0.649 0.825 9.582852 0.793 0.895 13.371720 0.610 0.803 8.939735 0.641 0.807 10.245

-1.00 -0.50 0.00 0.50 1.00





Costa 2007 140 0.800 0.731 0.853 12.859Costa 2008 99 0.800 0.716 0.861 10.764Ansari 2011 100 0.610 0.470 0.720 6.982Naghdi 2015 100 0.830 0.757 0.883 11.702Chansirinukor 2015 111 0.680 0.565 0.769 8.616

0.755 0.670 0.821 11.012

-1.00 -0.50 0.00 0.50 1.00

Figure 5. Meta-analysis on correlationcoefficient between Functional RatingIndex and Roland-Morris Disability Ques-tionnaire in low back pain.



Childs 2005 131 0.670 0.563 0.755 9.173Ansari 2011 100 0.720 0.610 0.803 8.939Wei 2012 115 0.958 0.940 0.971 20.330Chansirinukor 2015 111 0.780 0.695 0.844 10.864

0.825 0.583 0.932 4.553

-1.00 -0.50 0.00 0.50 1.00

Figure 6. Meta-analysis on correlationcoefficient between Functional RatingIndex and Oswestry Disability Index inlow back pain.



Ansari 2012 100 0.725 0.616 0.807 9.042Wei 2015 122 0.860 0.805 0.900 14.109Naghdi 2016 100 0.940 0.912 0.959 17.118

0.866 0.700 0.943 5.745

-1.00 -0.50 0.00 0.50 1.00

Figure 7. Meta-analysis on correlationcoefficient between Functional RatingIndex and pain intensity in neck pain.


intensity, showed by fair-quality investigations.34,36 Threefair-quality studies found that both the FRI and RMDQ hadcomparable test-retest reliability, although one study foundthat both were not positive.31,34,36 For other measurementproperties, information was limited owing to a limited num-ber of studies and low methodological quality.

DISCUSSIONStrong evidence showed that the FRI is a unidimensionalquestionnaire that has positive internal consistency in SPand LBP patients (Table 3). Consistently moderately

Study name Statistics for each study Corre


Ansari 2012 100 0.720 0.610 0.803 8.939Wei 2015 122 0.770 0.686 0.834 11.130Naghdi 2016 100 0.995 0.993 0.997 29.492Chansirinukor 2015 84 0.750 0.638 0.831 8.757

0.900 0.449 0.986 2.915

-1.00 -0.50



positive levels of evidence for test-retest reliability have beenfound in SP, LBP, and NP. Furthermore, moderate evidenceshowed that the FRI has a positive correlation with otherquestionnaires measuring the same physical functioning.For other measurement properties in in SP, LBP, and NP,the levels of evidence were limited, conflicting, or unknownowing to a limited number of studies and low methodologi-cal quality. Moreover, although one of the original objec-tives of developing the FRI was to use one questionnaireinstead of separate instruments for patients with multi-region pain, we only found research conducted on the entire

lation and 95% CI

0.00 0.50 1.00

Figure 8. Meta-analysis on correlationcoefficient between Functional RatingIndex and Oswestry Disability Index inneck pain.

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TABLE 3. Evidence Synthesis of Measurement Properties of FRI

Measurement Properties SP LBP NP

Structural validity Strong (þ) Strong (þ) Conflicting (�)

Internal consistency Strong (þ) Strong (þ) Conflicting (�)

Test-retest reliability Moderate (þ) Moderate (þ) Moderate (þ)

Measurement error Limited (þ) Conflicting (�) Limited (þ)

Content validity ? ? ?

Hypothesis testing ? Moderate (þ) Moderate (þ)

Cross-cultural validity ? ? ?

Responsiveness Limited (þ) Conflicting (�) Conflicting (�)

� indicates negative; ?, unknown; þ, positive; �, conflicting; FRI, functional rating index; LBP, low back pain; NP, neck pain; SP, spinal pain.


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SP population or those with single-region pain and did notfind any research on patients with multiregion pain.

Two excellent-quality studies reported conflicting results onstructural validity of the FRI in NP.37,41 Ansari et al.37 showedthat the FRI had two latent factors named NP dysfunction, andLBP dysfunction. This might suggest that several items may notcorrelate well with the construct—physical functioning—ofNP patients. After discarding walking and standing, whichoriginated from the ODI, a unidimensional questionnaire forLBP patients,44 they found the remaining items unidimen-sional. Therefore, it is highly possible that walking and stand-ing are not relevant to the physical functioning of NP patients.Naghdi et al.41 assessed measurement properties of the FRI inathletes with NP while Ansari et al.37 recruited patients fromphysiotherapy clinics. This may be another reason for thedifferent findings on structural validity.

Our meta-analysis showed that the FRI has positive test-retest reliability in LBP and NP. The sample sizes in thesestudies varied from 37 to 140 and resulted in a varied rangeof confidence intervals.24 Therefore, substantial heteroge-neity was found. In spite of the substantial heterogeneity, webelieve the FRI has positive test-retest reliability. In additionto this, another way to assess measurement error is tocompare the SDC with the minimal clinically importantdifference. A positive rating is given if the SDC or limit ofagreement is smaller than minimal clinically importantdifference.26 However, we did not perform these compar-isons because only one study estimated both.19

TABLE 4. Does FRI Have Comparable or Better MRegion-specific Questionnaires?

Measurement properties ODI

Internal consistency ?

Test-retest reliability Limited (�)

Measurement error Limited (þ)

Content validity ?

Structural validity ?

Hypothesis testing Limited (þ)

Cross-cultural validity ?

Responsiveness Strong (þ)

� indicates negative; ?, unknown; þ, positive; �, Conflicting; FRI, functional ratinODI, Oswestry Disability Index; RMDQ, Roland-Morris Disability Questionnaires S

Spine


The construct of the FRI is to measure physical function-ing of SP patients.14 However, the pooled correlationbetween the FRI and pain intensity showed a high Pearson’sr in addition to high correlation with the ODI, RMDQ, andNDI. The construct of pain intensity is different from theconstruct of physical functioning. The previous reviews havefound that the pain intensity is moderately correlated withthe NDI and RMDQ.12,27 Therefore, we hypothesize thatthe FRI may measure not only patients’ physical functioningbut also pain. In other words, the FRI may have a broaderconstruct than that of the NDI, RMDQ, and ODI.

There was strong evidence that the FRI’s responsivenessis comparable with the ODI and NDI (Table 4). There wasmoderate evidence showing that the FRI has comparabletest-retest reliability and hypothesis testing supported byconsistent findings across studies. Limited evidence wasfound for comparisons on test-retest reliability, measure-ment error, and hypothesis testing between the FRI, ODI,RMDQ, and NDI owing to the limited number of studies orlimited number of those with high methodological quality.More than half the measurement properties were rated asunknown because either no study or only poor-qualitystudies investigated them. Overall, there was limited evi-dence showing that the FRI has comparable measurementproperties with the ODI, RMDQ, or NDI.

A limitation of the current review is that only studiespublished in English were searched. Though we have alsosearched in Chinese databases, there were no related articles

easurement Properties Compared With Other

RMDQ NDI

? ?

Moderate (þ) Limited (þ)

Limited (þ) ?

? ?

? ?

Moderate (þ) ?

? ?

? Strong (þ)

g index; LBP, low back pain; NDI, Neck Disability Index; NP, neck pain;P, spinal pain.




available. We may have omitted studies published in otherlanguages and do not know how much risk of bias hasresulted from this. Furthermore, the FRI had been translatedinto several languages. We suggest that researchers applyingRasch and confirmatory factor analysis to verify whether theconstructs of these translated versions of the FRI are con-sistent with the original English version.

CONCLUSIONThere was strong evidence showing that the FRI is positiveon structural validity and internal consistency in SP and LBPwhile the evidence on structural validity and internal con-sistency in NP was conflicting. In addition, the evidence onthe measurement error, content validity, cross-culturalvalidity, and responsiveness were limited, conflicting, oreven unknown. A firm conclusion is hard to be drawn,and more high-quality researches should be conducted toassess several measurement properties whose current evi-dence is conflicting or unknown. We suggest using the FRIwith caution until further studies with high methodologicalquality support that it is positive in all measurement prop-erties, especially in patients with NP. We also suggestevaluating the FRI’s measurement properties in patientswith multi-region pain. Whether the FRI is a substitutefor the ODI, RMDQ, and NDI is still questionable. Morehead-to-head comparison studies with high methodologicalquality are needed.

E1

Co

Key Points

348

py

The FRI is a unidimensional questionnaire and haspositive internal consistency and structuralvalidity in patients with SP and patients with LBP.

The evidences for most measurement properties ofthe FRI are limited, conflicting, or even unknown.

The FRI is comparable with other questionnaires ina few measurement properties, but the majority isunknown, conflicting, or even unknown.

The FRI should be used with caution until thereare more studies with high methodological qualitythat support the view that it is positive in allmeasurement properties.

rig

Supplemental digital content is available for this article.Direct URL citations appearing in the printed text areprovided in the HTML and PDF version of this article onthe journal’s Web site (www.spinejournal.com).

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