Diagnostic accuracy test for the hypoxia-altitude simulation test (HAST) by oxygen saturation measured by pulse oximetry (SpO2) or arterial oxygen tension (PaO2) cut-offs
| Positive HAST according to: | ||
| Cut-off SpO2 <85% | Cut-off PaO2 <6.6 kPa | |
| Apparent prevalence (HAST positive/all patients) | 0.36 (0.25–0.48) | 0.19 (0.10–0.30) |
| True prevalence (ARAHE present/all patients) | 0.67 (0.55–0.77) | 0.69 (0.56–0.80) |
| Sensitivity (TP/(TP+FN)) | 0.46 (0.32–0.61) | 0.25 (0.13–0.40) |
| Specificity (TN/(TN+FP)) | 0.84 (0.64–0.95) | 0.95 (0.75–1.00) |
| Positive predictive value (TP/(TP+FP)) | 0.85 (0.66–0.96) | 0.92 (0.62–1.00) |
| Negative predictive value (TN/(TN+FN)) | 0.44 (0.29–0.59) | 0.37 (0.24–0.51) |
| Positive likelihood ratio (sensitivity/1 − specificity) | 2.87 (1.12–7.41) | 5.00 (0.69–36.13) |
| Negative likelihood ratio (1 − sensitivity/specificity) | 0.64 (0.47–0.87) | 0.79 (0.65–0.96) |
| Proportion of correctly classified patients | 0.59 (0.47–0.70) | 0.47 (0.34–0.60) |
Cut-off values for a positive HAST are set as SpO2 <85% and/or PaO2 <6.6 kPa according to the British Thoracic Society (BTS) [14]. Positive ARAHE is defined as development of acute mountain sickness, need of oxygen therapy due to severe hypoxaemia (resting SpO2 <80% >30 min or <75% for >15 min) or any other intercurrent illness needing treatment such as chest pain, severe dyspnoea, arrhythmia, hypertensive crisis or others (see text) [19]. ARAHE: altitude-related adverse health effects; TP: true positive; FP: false positive; FN: false negative; TN: true negative.