Table 5.
SpCO Predictive Performance (0% < %COHb < 15%). Both Carboxyhemoglobin Probesf
| “Positive” | %COHb ≥ 10% | %COHb ≥ 5% | %COHb ≥ 10% | |||||
|---|---|---|---|---|---|---|---|---|
| SpCO Threshold | ≥ 10% | ≥ 5% | ≥ 6.6 | ≥ 5% | ||||
| SaO2 Range | 95–100% | 90–95% | 85–90% | 95–100% | 90–95% | 85–90% | All | All |
| Observations | 177 | 72 | 32 | 177 | 72 | 32 | 283 | 283 |
| PPV = TP/(TP+FP) | 78.0% | 100.0% | 100.0% | 90.0% | 83.3% | 75.0% | 72.9% | 62.1% |
| NPV = TN/(TN+FN) | 76.5% | 50.0% | 52.4% | 68.4% | 77.8% | 50.0% | 79.7% | 79.7% |
| Sensitivity = TP/(TP+FN) | 50.0% | 43.5% | 52.4% | 85.7% | 91.8% | 71.4% | 77.9% | 92.4% |
| Specificity = TN/(TN+FP) | 92.0% | 100.0% | 100.0% | 76.5% | 60.9% | 54.5% | 75.0% | 51.3% |
|
| ||||||||
| Accuracy = (TP+TN)/(P+N) | 76.8% | 63.9% | 68.8% | 83.1% | 81.9% | 65.6% | 76.3% | 70.3% |
SpCO, percentage of carboxyhemoglobin as measured by the Masimo pulse CO-oximeter; %COHb, percentage of carboxyhemoglobin measured in arterial blood; SaO2, arterial blood oxygen saturation; PPV=Positive Predictive Value, NPV=Negative Predictive Value, TP=True Positive, FFP=false Positive, TN=True Negative, FN=False Negative. SpCO=6.6 was the cutoff optimizing sensitivity and specificity by receiver-operator characteristics analysis.