Reliability and Construct Validity of Self-Report Questionnaires for Patients With Pelvic Girdle Pain

Tables

Table 1.

Baseline Characteristics of Participants in Total Sample and in Test-Retest Subsample

^a Employed category included participants who reported that they were on sick leave or maternity leave.
^b 8-Item SF-36=8-item version of the Medical Outcomes Study 36-Item Short-Form Health Survey questionnaire, role–physical=role of physical health problems in work or other daily activities, role–emotional=role of emotional problems in work or other daily activities. Higher scores indicate better health.

Table 2.

Missing Data, End Effects, and Internal Consistency for the Instruments

^a Cronbach α value for sum scores (bold type) and item-total correlations for single items.
^b The scores were summarized and recalculated as scores of 0 (no problem at all) to 100 (maximum problem). VAS=visual analog scale.
^c The scores were summarized to yield scores of 0 (totally disagree=no fear avoidance) to 24 (totally agree=maximum fear avoidance). Item 1 scores were not included in the summary score.
^d The scores were summarized to yield scores of 0 (no pain catastrophizing) to 52 (maximum pain catastrophizing).
^e 8-Item SF-36=8-item version of the Medical Outcomes Study 36-Item Short-Form Health Survey questionnaire, role–physical=role of physical health problems in work or other daily activities, role–emotional=role of emotional problems in work or other daily activities. Different ordinal scales were used for the individual subscales (0=best score, 4 or 5=poorest score). The scores were summarized and recalculated to scores of 0 (poor health) to 100 (excellent health). Cronbach α values could not be computed for the subscales of the 8-item version of the SF-36.

Table 3.

Test and Retest Scores, Measurement Error, and Intraclass Correlation Coefficient (ICC)^a

↵^a SEM=standard error of measurement, MDC_ind=minimal detectable change at the individual level, MDC_group=minimal detectable change at the group level, CI=confidence interval.
^b The Fear-Avoidance Beliefs Questionnaire and the Pain Catastrophizing Scale also are presented as rescaled scores to allow comparisons of test-retest reliability results.
^c 8-Item SF-36=8-item version of the Medical Outcomes Study 36-Item Short-Form Health Survey questionnaire, role–physical=role of physical health problems in work or other daily activities, role–emotional=role of emotional problems in work or other daily activities. Higher scores indicate better health.

Table 4.

Correlations Between Instruments^a

↵^a PGQ=Pelvic Girdle Questionnaire, DRI=Disability Rating Index, ODI=Oswestry Disability Index, FABQ=Fear-Avoidance Beliefs Questionnaire, PCS=Pain Catastrophizing Scale, 8-item SF-36=8-item version of the Medical Outcomes Study 36-Item Short-Form Health Survey questionnaire, role–physical=role of physical health problems in work or other daily activities, role–emotional=role of emotional problems in work or other daily activities.
^b Higher scores indicate better health.

Table 5.

Construct Validity: Seven A Priori Formulated Hypotheses and Correlation Values^a

↵^a All correlations were significant at the .01 level (2-tailed). Values of less than .3 indicate low correlations, those between .3 and .6 indicate moderate correlations, and those of greater than .6 indicate high correlations. PGQ=Pelvic Girdle Questionnaire; DRI=Disability Rating Index; ODI=Oswestry Disability Index; SF1, SF2, SF3, SF4, SF5, SF6, SF7, and SF8=general health, physical functioning, role–physical (role of physical health problems in work or other daily activities), bodily pain, vitality, social functioning, mental health, and role–emotional (role of emotional problems in work or other daily activities) items of the 8-item version of the Medical Outcomes Study 36-Item Short-Form Health Survey questionnaire, respectively; FABQ=Fear-Avoidance Beliefs Questionnaire; PCS=Pain Catastrophizing Scale.

Table 6.

Comparison of Instrument Scores According to Pregnancy and Pain Localization by Receiver Operating Characteristic Curve Analysis^a

↵^a AUC=area under the curve, CI=confidence interval, 8-item SF-36=8-item version of the Medical Outcomes Study 36-Item Short-Form Health Survey questionnaire, role–physical=role of physical health problems in work or other daily activities, role–emotional=role of emotional problems in work or other daily activities.