Changing measurement instrument at follow-up: a potential source of error

Area of Science:

• Neurology
• Clinical Research Methodology

Background:

• Many headache studies utilize phone interviews for long-term follow-up data collection.
• Systematic self-observation is often employed for other data points in these studies.
• Potential calibration discrepancies between these two methods are a concern for internal validity.

Purpose of the Study:

• To assess the comparability of headache activity data collected via phone versus systematic self-observation.
• To determine if calibration differences between methods compromise internal validity in headache research.

Main Methods:

• Twenty-six participants with tension headaches were involved in the study.
• Participants reported headache activity over the phone.
• Participants also systematically charted their headache activity.

Main Results:

• Significant calibration differences were identified between phone reporting and self-charted headache data.
• These discrepancies indicate that the two measurement methods are not directly comparable.
• The findings suggest limitations in the internal validity of studies relying on phone data for follow-up.

Conclusions:

• Direct comparison of phone-reported and self-observed headache data is not advisable due to calibration issues.
• The use of phone data for long-term headache follow-up may jeopardize study conclusions.
• Recommendations for alternative or improved follow-up methodologies are discussed.