Figure 1.

Frequency of reporting of pain or burning above the belly button in the normative survey. The histograms show the frequency of reporting in different time frames for men, women and the combined sample. The vertical dotted line shows the 90th percentile for the combined sample of females and males. MT shows the minimum threshold in males and FT shows the minimum 90th percentile in females. Accordingly, a threshold of only 2–3 days a month would limit misclassification to 10% in females, whereas a threshold of 1 day/ month would limit misclassification to 10% in males. Reproduced with permission from Rome Foundation, Inc.