Table 2.
Percent agreement between RT- PCR results and MALDI-ToF results as determined by cutoff AUC values. Cutoff values for each biomarker peak were based on sorting all specimen AUC values for each feature (m/z peak ranges) and setting a threshold AUC value that separated COVID-19 positive from COVID-19 negative results.
| (Ig heavy chain/amylase)+2 | Cutoff AUC: 5.2E + 06 | |
| (27,900–29,400 m/z) | COVID-19 Positive | COVID-19 Negative |
| MALDI-ToF Positive | 96.67% | 10.00% |
| MALDI-ToF Negative | 3.33% | 90.00% |
| Ig heavy chain/amylase | Cutoff AUC: 4.0E + 07 | |
| (55,500–59,000 m/z) | COVID-19 Positive | COVID-19 Negative |
| MALDI-ToF Positive | 96.67% | 10.00% |
| MALDI-ToF Negative | 3.33% | 90.00% |
| Spike protein S2/immune protein | Cutoff AUC: 1.5E + 06 | |
| (66,400–68,100 m/z) | COVID-19 Positive | COVID-19 Negative |
| MALDI-ToF Positive | 100.00% | 6.67% |
| MALDI-ToF Negative | 0.00% | 93.33% |
| Spike protein S1 | Cutoff AUC: 1.0E + 06 | |
| (78,600–80,500 m/z) | COVID-19 Positive | COVID-19 Negative |
| MALDI-ToF Positive | 93.33% | 10.00% |
| MALDI-ToF Negative | 6.67% | 90.00% |
| Asymptomatic Biomarker | Cutoff AUC: 1.2E + 06 | |
| (111,500–115,500 m/z) | COVID-19 Positive | COVID-19 Negative |
| MALDI-ToF Positive | 93.33% | 10.00% |
| MALDI-ToF Negative | 6.67% | 90.00% |