Construct validity and reliability of the Rivermead Post-Concussion Symptoms Questionnaire.
OBJECTIVE
To provide further evidence of reliability and internal and external construct validity of the Rivermead Post-Concussion Symptoms Questionnaire (RPQ), which measures severity of postconcussion symptoms following head injury.


METHODS
A cross-sectional study of consecutive patients presenting with a head injury in two urban teaching hospitals and a community trust.


METHODS
Three hundred and sixty-nine patients returned a questionnaire from 1689 consecutive adult patients (18 years and above) referred to radiology for a skull X-ray following a head injury, and those who were currently under the care of a community-based multidisciplinary head injury team.


METHODS
Internal construct validity tested by fit to the Rasch Measurement model; external construct validity tested by correlations with Rivermead Head Injury Follow-up Questionnaire (RHFUQ); test-retest reliability tested by correlations at two-week intervals.


METHODS
Rivermead Post-Concussion Symptoms Questionnaire and Rivermead Head Injury Follow-up Questionnaire.


RESULTS
RPQ scores ranged from 0 to 64 (17.3% floor, 0.3% ceiling). Overall fit to the Rasch model was poor (item fit mean -0.416, SD = 1.989, chi-squared= 172.486, p<0.01) suggesting a lack of unidimensionality. The items headaches, dizziness and forgetful displayed misfitting residuals and the first two items also displayed significant item trait fit statistics (p < 0.0006). After removing the items headaches, dizziness and subsequently nausea the RPQ demonstrated good fit at overall and individual item levels, both for the remaining 13 items (RPQ-13) and the three items (RPQ-3) which now formed a subsidiary scale. All items functioned consistently across age and gender. The RPQ-13 and RPQ-3 scales showed test-retest reliability coefficients of 0.89 and 0.72 (both p-values < 0.01) and positive correlations with RHFUQ scores (0.83 for RPQ-13, 0.62 for RPQ-3, both p-values < 0.01).


CONCLUSIONS
As currently used, the RPQ does not meet modern psychometric standards. Its 16 items do not tap into the same underlying construct and should not be summated in a single score. When the RPQ is split into two separate scales, the RPQ-13 and the RPQ-3, each set of items forms a unidimensional construct for people with head injury at three months post injury. These scales show good test-retest reliability and adequate external construct validity.
Eyres
Sophie
S
Academic Unit of Musculoskeletal and Rehabilitation Medicine, The University of Leeds, 36 Clarendon Road, Leeds LS2 9NZ, UK.
Carey
Amy
A
Gilworth
Gill
G
Neumann
Vera
V
Tennant
Alan
A
D000293:Adolescent; D000328:Adult; D006259:Craniocerebral Trauma / Q000150:complications*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D038223:Post-Concussion Syndrome / Q000175:diagnosis*; D011594:Psychometrics; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires