Validity of a measure of the frequency of headaches with overt neck involvement, and reliability of measurement of cervical spine anthropometric and muscle performance factors

Objective: To test the validity of a questionnaire to measure frequency of headaches related to the neck. A secondary goal was to test the reliability of field measurement of associated cervical spine anthropometric and muscle performance factors. Design: Intermethod and test-retest comparisons. Setting: Two municipalities in a rural area of Tasmania, Australia. Participants: One hundred subjects were selected as a representative sample of never-injured adults from a comprehensive listing of the source population, and 93 participated. Main Outcome Measures: Subjects distinguished headaches matching three criteria for overt neck involvement, reported past-month frequency by questionnaire, and recorded in a diary occurrences during the next month. Measurements of height, weight, neck column length and circumference, lateral flexion and extension range of movement, cervical short flexor muscle endurance, and cervical long flexor and extensor strength were taken at the start and end of the month. Results: Headache frequency was associated with neck stiffness and neck ache. There was moderate agreement (weighted κ = .66) between questionnaire and diary, but better agreement (κ = .72) for subjects who maintained their usual patterns of recreational sport. For this group, the correlation with 'true' frequency was r(u) = .87. The anthropometric and muscle performance factors were reliably measured (intraclass correlations .96 to 1.00, κ .78 to .86) despite minor improvement in muscle performance on retest. Conclusions: The questionnaire measure has construct validity. Neck-related headaches are a temporally stable presentation in never-injured subjects who maintain customary sporting activity. Measurement error was consequential, but less so for this group than for the study subjects generally. The anthropometric and muscle performance measurements were reliable, but slight improvements on retest suggest the need for multiple measurements. (C) 2000 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation.