Table 5 Factor analysis matrix of RDQ items in three factors (heartburn, regurgitation and epigastric pain).

   Burning behind breastbone – severity

0.84

0.22

0.31

   Burning behind breastbone – frequency

0.84

0.11

0.37

   Pain behind breastbone – severity

0.25

0.05

0.80

   Pain behind breastbone – frequency

0.10

0.04

0.84

Regurgitation

   Acid taste – severity

-0.09

0.89

0.16

   Acid taste – frequency

-0.07

0.84

0.15

   Movement of materials – severity

0.33

0.72

0.17

   Movement of materials – frequency

0.36

0.72

0.17

Epigastric pain

   Upper stomach burning – severity

0.31

0.12

0.59

   Upper stomach burning – frequency

0.36

0.01

0.63

   Upper stomach pain – severity

-0.18

0.27

0.83

   Upper stomach pain – frequency

-0.15

0.14

0.88