Once the interviewer had a thorough description and understanding of the participant’s cold, the participant was asked to complete the questionnaire-in-development. After marking answers on the questionnaire (which took 3 to 5 minutes), each participant was asked to comment on its ease of use, item wording, formatting, and response range as well as whether it accurately and comprehensively measured the symptoms and functional impact they were experiencing. The instrument development phase of the interview lasted for another 20 to 30 minutes.
We used focus group methods in the final month of the study as an additional window into participants’ experiences.54-56 The focus groups used the same inclusion criteria as the long interviews and followed the same general format, first using open-ended questions to elicit symptoms and their impact, then administrating the questionnaire and discussing item inclusion and formatting. However, we encouraged discussion rather than self-assessment, as the focus group methodology derives its strength from the interactive nature of conversation. For instance, a statement made by one participant would spark interest or recall in another, thereby generating a richer, fuller, and more representative description of symptoms and functional impact.
Individual interviews were held by 1 of 5 trained interviewers (B.B., L.L., R.M., E.S., J.S.). All 3 focus groups were run by the lead author, with at least 1 other research team member assisting. Interviews and focus groups were arranged as soon as possible after the initial telephone contact so that participants would still have cold symptoms while being interviewed. All interviews and focus groups were discussed in biweekly group meetings. Decisions on item inclusion, wording, and questionnaire format were made by research group consensus. Several versions of the questionnaire were brought back to cold-sufferers for further cognitive testing. The diversity of interviewers and respondents provided protection against personal bias in ascertaining and interpreting symptoms and impairments.
TABLE 1
QUESTIONS ASKED DURING INTERVIEW
| Current Symptom History and Evaluation |
|---|
| List and describe all symptoms you have with this cold. |
| How do these symptoms bother you? |
| What is the first symptom you noticed when getting this cold? The Next? |
| The next? |
| Which cold symptom bothers you the most? How and why? |
| Are there other symptoms that bother you? How and why? |
| Interventions |
| What do you do to relieve cold symptoms? Why? |
| What over-the-counter medicines would you use? Why? Did it help? |
| What herbal medicines would you use? Why? Did it help? |
| Do you do anything else to relieve symptoms or treat your cold? Why? |
| Did it help? |
| When would you see a doctor or other health care provider? Why? |
| Lifestyle |
| Has this cold interfered with your normal activities? How? |
| When does a cold keep you from doing what you want or need to do? How? |
| Describe what things are harder to do? |
| Previous Symptom History and Evaluation |
| How many colds did you have this past year? |
| How long did they usually last? |
| List and describe what symptoms you usually get with your colds? |
| How do these symptoms bother you? |
| Survey Evaluation (After Participant Has Completed the Questionnaire) |
| Is this form easy to read? |
| Are there any other symptoms that should be on this questionnaire? |
| Are there any questions that shouldn’t be there? |
| Are there any questions that could be worded better? |
| Is the 7-point scale appropriate? Why or why not? |
Results
Phase 1
Of the 148 college students enrolled, 142 followed protocol and were included in the analysis. Of the 853 person-days documented, 546 (64%) were covered by both data systems; 287 (33.6%) came from paper surveys only; and 18 (2.1%) were filled out via computer only. Because only 2 (0.2%) questionnaires were missing any data, our data capture rate was 99.8%. Comparing data from the computerized and paper data sources provided evidence of consistency. Of the 546 days in which both paper and computer instruments provided data, 512 yielded identical responses (94% concordant) to the global severity of illness question. Of the 34 (6%) discrepancies, 29 were off by 1 point on the 9-point Likert-type scale and 5 discrepancies were off by 2 points. Comparing computer and paper responses with the 15 specific symptom questions also yielded high levels of concordance. Of 8190 item responses, 7777 (95%) were concordant, while 413 (5%) were classified as data discrepancies. Of these, 293 were off by 1 point on the 9-point scale; 68 were off by 2 points; 27, by 3 points; 17, by 4 points; 7, by 5 points; and 1 by 6 points.
Factor analysis of the data provided further evidence of internal validity. Structural equation modeling techniques57,58 were used to model symptom severities over time. A 4-dimensional symptom-recovery model (df = 71; P = .000025) provided a goodness of fit index of 0.88, a root mean square residual of .095, and a chi-squared/df ratio of 139/71 = 1.95. From the pool of 15 scaled symptom scores, 14 items contributed significantly to the model. (In this data set, loss of appetite was an infrequent symptom contributing insignificantly toward the model, and was dropped.) The 14 symptoms naturally aggregated into 4 underlying symptomatic dimensions: cough, throat, nasal, and fever and aches. Table 2 provides the reliability coefficients, standardized item loading coefficients, and standard errors of these loadings for the 4 dimensions. The reliability coefficients of the symptom dimensions were calculated using a procedure proposed by Dillon and Goldstein.59 Scale recovery curves, generated using a mixed modeling approach,60,61 were internally predictive, responsive,37,62 and consistent with what is known about the natural history of URI.