Table 2

Sensitivity, specificity and correct classification rates (%) of measures of secondhand smoke exposure

Own homeRelative's homeFriend's homeAutomobile4-Item scale3-Item scale
24 h7 days24 h7 days24 h7 days24 h24 h7 daysHome smoking rules
>0.05 ng/mL
 Correct classification76.275.471.272.472.075.074.574.673.869.5
>0.215 ng/mL
 Correct classification89.987.389.888.890.789.893.288.183.976.3
>0.80 ng/mL
 Correct classification88.986.594.193.191.592.294.085.683.175.6
  • The 3-item scale combines past 7-day SHS exposure in the residence of one's own, of friends and of relatives; the 4-item scale combines past 24-h residential SHS exposure with automobile SHS exposure. For examination of correct classification, sum scores of 1 or greater on these scales were coded as exposed (1) versus not exposed (0).

  • Bold font shows classification rates for the item that outperformed the other measures.

  • SHS, secondhand smoke.