Tests performed | Cost resource units# | Cases identified | Cases missed | Cost/case identified | Marginal cost per case identified relative to base | ||||||
Questionnaires | PEFs | Spirometries | Questionnaires | PEFs | Spirometries | Total cost | |||||
Moderate/severe | |||||||||||
1. Spirometry only | 1000 | 0 | 0 | 4000 | 4000 | 80 | 0 | 50.0 | 163.7 | ||
2. CART questions only | 1000 | 0 | 554 | 1000 | 0 | 2216 | 3216 | 70 | 10 | 45.9 | 448.0 |
3. A priori questions only | 1000 | 0 | 802 | 1000 | 0 | 3208 | 4208 | 78 | 2 | 53.9 | 212.4 |
4. PEF only | 0 | 1000 | 218 | 0 | 1000 | 872 | 1872 | 67 | 13 | 27.9 | |
5. Staged: a priori questions, then PEF in subgroup | 1000 | 802 | 178 | 1000 | 802 | 712 | 2514 | 66 | 14 | 38.1 | -642.0¶ |
Severe | |||||||||||
1. Spirometry only | 1000 | 0 | 0 | 4000 | 4000 | 35 | 0 | 114.3 | 1320.0 | ||
2. CART questions only | 1000 | 0 | 196 | 1000 | 0 | 784 | 1784 | 25 | 10 | 71.4 | -53.0¶ |
3. A priori questions only | 1000 | 0 | 738 | 1000 | 0 | 2952 | 3952 | 34 | 1 | 116.2 | 2592.0 |
4. PEF only | 0 | 1000 | 90 | 0 | 1000 | 360 | 1360 | 33 | 2 | 41.2 | |
5. Staged: a priori questions, then PEF in subgroup | 1000 | 738 | 81 | 1000 | 738 | 324 | 2062 | 32 | 3 | 64.4 | -702.0¶ |
Data are presented as n. PEF: peak expiratory flow; CART: classification and regression tree. #: resource unit = 10 min of nurse/technician time; ¶: marginal costs per case are negative for algorithms that identify fewer cases than PEF only.