Table 2. Comparison of iron deficiency classifications.
| Median | Lower quartile (Q1) | Upper quartile (Q1) | ||||||||||
| No ID | ferr<15 | ferr <20 | iron <11 | No ID | ferr<15 | ferr <20 | iron <11 | No ID | ferr<15 | ferr <20 | iron <11 | |
| Age (yr) | 48 | 47.5 | 47.5 | 52 | 35 | 37.5 | 39 | 43 | 62 | 52.5 | 54 | 61 |
| SaO2 (%) | 95 | 95 | 94.6 | 94.9 | 92 | 90.5 | 89.3 | 92 | 96.5 | 96 | 95.5 | 95.8 |
| BMI (kg/m2) | 25.8 | 25.1 | 25.3 | 26.3 | 22.9 | 21.9 | 21.9 | 21.9 | 28.2 | 28.3 | 29.8 | 30.2 |
| Haemoglobin (g/dl) | 15.1 | 12.8 | 12.9 | 13 | 13.9 | 11.6 | 12.3 | 11.9 | 16 | 13.7 | 13.8 | 14.2 |
| Haematocrit | 0.44 | 0.4 | 0.4 | 0.4 | 0.41 | 0.38 | 0.39 | 0.38 | 0.47 | 0.42 | 0.43 | 0.44 |
| MCV (fl) | 89.6 | 84.8 | 85 | 85 | 86.8 | 73.4 | 73.9 | 76.4 | 92.8 | 86.9 | 87.4 | 87.4 |
| MCH (pg) | 30.7 | 26.6 | 27.2 | 27.6 | 29.4 | 22.6 | 22.8 | 23.9 | 31.8 | 29 | 29.1 | 29.2 |
| MCHC (g/dL) | 34 | 32.1 | 32.2 | 32 | 33.3 | 30.7 | 30.6 | 31 | 34.7 | 33.1 | 33.4 | 33.2 |
| Serum iron (µmol/L) | 18 | 7 | 8.5 | 7 | 16 | 4 | 4 | 4 | 24 | 13 | 13 | 10 |
| Serum TfSI (%) | 30.5 | 10.5 | 15 | 11 | 27 | 6 | 6 | 6 | 44 | 17.5 | 21 | 15 |
| Serum ferritin µg/L | 51 | 7 | 9.5 | 19 | 31.5 | 5.5 | 6 | 7 | 93 | 10.5 | 14 | 40 |
| Oxygen content (mls/dl) | 18.8 | 16 | 16 | 16.3 | 17.4 | 14.9 | 14.8 | 14.8 | 20.1 | 17.4 | 17.6 | 18.1 |
For patients presenting between 2006 and 2010, iron deficiency was assigned as absent (No ID) if ferritin, iron and TfSI were all clearly in the normal range (ferritin>20 µg/L, serum iron>11 µmol/L and TfSI>20%, N = 93). The groupings to examine iron deficiency were ferritin <15 µg/L (ferr<15, N = 20); ferritin <20 µg/L (ferr<20, N = 26); and serum iron <11 µmol/L (iron <11, N = 50). BMI, body mass index. MCV, mean corpuscular volume. MCH, mean corpuscular haemoglobin. MCHC, mean corpuscular haemoglobin concentration. TfSI, transferrin saturation index.