Table 2: Encoding of some prognostic factors.

Prognostic factorCoding

Sex0 (Male)1 (Female)
Residence0 (Urban)1 (Semiurban)2 (Rural)
Season of the symptoms0 (None)1 (Winter)2 (Autumn)3 (Spring)4 (Summer)5 (>2 Seasons)
Type of heating0
(Central heating)
1
(Wood stove)
2
(Oil stove)
3 (Fireplace)4
(Central heating + Fireplace)
Pregnancy duration in weeks0 (<37)1 (37-38)2 (>38)
Allergens0 (0)1 (3.5–6 mm)2 (>6 mm)