We sought to compare between the mean intakes total energy, energy contribution from macronutrients, and selected nutrients of patients with T2DM calculated using telephone interviews and a face-to-face interview in the dietary intake assessment by the 24-hour recall due to the lack of comparison between two interviews in this dietary intake assessment method. There were significant differences between the mean intakes in majority energy and selected nutrients intakes calculated using face-to-face interview versus the other interview approaches; all of three interviews versus two telephone interviews together; and all of three interviews versus a face-to-face interview with a similar pattern in the same nutrients. These comparisons were done between the mean intakes calculated using two telephone interviews and the mean intakes calculated using a face-to-face interview versus two telephone interviews together. Interestingly, no significant difference was found between the mean intakes calculated using two telephone interviews. However, some significant differences were revealed between the mean intakes calculated using a face-to-face interview and two telephone interviews together with a similar pattern in the previous same nutrients. In our study, the number of energy and selected nutrients intakes were important to be significant when two approaches compare with each other. First, our goal was to distinguish the feasibility of interviewing approaches which could reasonably provide more comprehensive and accurate results. In the same way, the literature review of previous limited studies showed the advantages and the disadvantages of applying these two approaches; however, in general, this conflict was evident in studies.
A few studies demonstrated that telephone approaches were a preferable option. They supposed that collecting 24-hour dietary recall data through telephone interviews was a practical and valid data collection tool. They indicated that one of the advantages of telephone assessment as one of the interview approaches for assessing usual dietary intake was cost-effectiveness this method as well as the ability data gathering from a large number of individuals [3, 5]. While, quantitative food frequency questionnaire as one of collecting methods of dietary intake data can be completed satisfactorily by telephone if interviews were conducted by expert and trained dietetic interviewers . On the other hand, some researchers revealed that the telephone interview was comparable with a face-to-face interview. They believed that both telephone and face-to-face interviews generated similar information and the data collected by telephone interview appeared to be interchangeable with dietary data collected by face-to-face interview [9, 10, 14, 15]. A necessary condition for this consistency and reliability was a structured interview or closed-ended questionnaire . The interviewer effect was the other limitation that leads to the vulnerability of the 24-hour dietary recall method . The most important issue is that the mean energy requirement of our patients might be higher than the calculated mean energy intake of patients through 24-hour recall assessment. The lower the calculated mean energy intake, the lower the calculated mean intake of the macronutrients and the micronutrients through 24-hour recall assessment. Therefore, our data in determining the mean intakes energy and selected nutrients in gathering data period might be underreported. However, the aim of this study was to compare the findings of the mean intakes calculated using face-to-face interviews with telephone interviews. The goal was the superiority and dominance of one method against another or the equality of one method with another.
We revealed that there was no significant difference between the two telephone interviews. One patient's intake may change from day to day. However, a nonsignificant change in two consecutive intakes in one method such as telephone interview is not accidental compared to the other approach. While there were significant differences in 18 energy and selected nutrients intakes of participants between a face-to-face interview and two telephone interviews together. Our study demonstrated that the telephone approach could not be considered as an alternative to the face-to-face approach for collecting dietary data by the 24-hour dietary recall method as an open-ended assessment. The total energy and nutrients intakes in face-to-face approaches were higher than two telephone approaches together and each of the telephone interviews. Therefore, each of the telephone interviews underestimates the total energy and nutrients intakes in the 24-hour dietary recall. In fact, this underestimation is due to underreporting total energy and selected nutrients of patients with T2DM in the study.
Our results were paralleled with the other researchers [8, 16, 17]. The response rate for food items in the face-to-face interview was greater; while, there was more data being deleted or missing data in the telephone interview . In another study, in order to compare different sampling methods in wine consumer research, Szolnoki and Hoffmann revealed that the face-to-face approach provided the most representative and realistic results. While, the telephone approach might provide a good alternative in collecting data from a larger sample . More complete population coverage for sampling, item response, completion of the questionnaire, survey response, length of verbal response/amount of information, and respondents' preferences for mode of administration were high for a face-to-face interview; however, these factors were low for a telephone interview. While interviewer bias for both of the interviews were high .
Our study had a few strengths. The only noticeable feature of this study was that it was novel in a situation where the researcher was not able to spend extra budget on a face-to-face interview, and especially in the COVID-19 pandemic and similar situations that the researcher will not able to contact or meet the patient directly. The other strengths include the population used and a large number of patients with T2DM for interview approach implementation. A study of this kind has not been conducted in people with T2DM living in Iran. We have not any special limitations in our study. Limitations include the fact that the order of the recalls was not randomized and the face-to-face recall was always conducted first. However, some factors such as mood, attention, spirit, and intelligence are the integral parts of this kind of dietary intake assessment. On the other hand, in face-to-face interviews, interviewees might explain daily food intake in more detail. Therefore, food intakes were underestimated in telephone interviews. We attempted to adjust these factors in both face-to-face and telephone interviews through the expert interviewer. Our research has provided evidence of the advantage of a face-to-face approach in the dietary intake assessment by the 24-hour recall in patients with T2DM. Therefore, the superiority of an approach to another approach depends on the study design and the tools used.