Table 1.
Factors associated with steady-state, averaged hemoglobin first and last quartile (HbQ1 & HbQ4). Univariable analysis using logistic regression for association with HbQ1, adjusting for multiple sample observations.
| Total sample observations | Low steady state Hgb (HbQ1) | High steady state Hgb (HbQ4) | OR [95% CI] P-value | |
|---|---|---|---|---|
| Sex (total group n = 269) | ||||
| Male | 150 | 89 (66·4%) | 61 (45·2%) | 2·40 [1·28–4·50] 0·006 |
| Age category (on day of sample) | 269 | |||
| 1–3 years | 3 (2·4%) | – | 0·94 [0·60–1·47] 0·792 | |
| 4–6 years | 15 (11·2%) | 22 (16·3%) | ||
| 7–12 years | 93 (69·4%) | 86 (63·7%) | ||
| 13–17 years | 23 (17·2%) | 27 (20·0%) | ||
| Inflammatory markers | ||||
| WBC (x 109/L) | 264 | 14·4 (11·85–17·15) | 12·5 (9·82–16·30) | 4·80 (2·0.00–11·53) <0.001 |
| AGP (mg/dL) | 266 | 125·93 [97·41–158·08] | 117·86 [88·85–144·72] | 1·30 [0·62–2·71] 0·482¶ |
| AGP elevated [>120 mg/dL] | 68 (51·5%) | 64 (47·8%) | 1·16 [0·70–1·94] 0·566 | |
| CRP [mg/L] | 266 | 4·19 [2·29–8·40] | 3·98 [1·85–6·98] | 1·12 [0·89–1·43] 0·324¶ |
| CRP elevated [≥ 3 mg/L] | 82 (62·1%) | 84 (62·7%) | 0·98 [0·57–1·68] 0·930 | |
| Potential iron markers | ||||
| Ferritin (μg/L) | 266 | 116·65 [57·75–229·35] | 163·15 [87·70–254·70] | 0·79 [0·59–1·05] 0·102¶ |
| Transferrin (g/L) | 266 | 3·03 [2·52–3·65] | 2·88 [2·53–3·54] | 1·13 [0·84–1·51] 0·435 |
| Transferrin saturation [%] | 263 | 26·98 [18·61–40·31] | 26·42 [18·98–36·14] | 1·01 [0·99–1·03] 0·315 |
| sTfR (mg/L) | 259 | 15·01 [10·88–62·64] | 13·24 [9·01–51·38] | 1·00 [0·997–1·013] 0·257 |
| sTfR-F index | 256 | 3·42 [2·17–11·60] | 2·98 [1·73–10·06] | 1·02 [0·98–1·06] 0·283 |
| Hypoferritinaemia (ferritin <30 μg/L) | 15 (11%) | 10 (7%) | 1·59 [0·66–3·83] 0·301 | |
| sTfR-F index>5·6 [32] | 51 (40·8%) | 58 (44·3%) | 0·87 [0·53–1·42] 0·574 | |
| Transferrin saturation < 16% | 21 (16%) | 20 (15%) | 1·07 [0·53–2·17] 0·853 | |
| Red cell indices | ||||
| MCV (fL/cell) | 264 | 84·00 [78·50–87·45] | 79·00 [71·50–85·00] | 1·03 [0·97–1·08] 0·323 |
| MCHC (g/dL) | 260 | 32·30 [31·40–33·20] | 32·30 [31·50–33·20] | 0·970 [0·856–1·10] 0·637 |
| Microcytic MCVa | 50 (38%) | 79 (60%) | 0·41 [0·23–0·72] 0·002 | |
| MCHC <32 g/dL | 48 (37%) | 51 (39%) | 0·99 [0·73–1·32] 0·962 | |
| Erythropoietic drive | ||||
| EPO [μIU/mL] | 241 | 110·42 [76·95–207·41] | 54·96 [36·88–81·47] | 1·009 [1·001–1·016] 0·016 |
| Reticulocyte [%] | 151
|
12.9 [9·3–16·2] | 10.2 [6·2–15·8] | 1·05 [1·00–1·10] 0·036 |
| Hemolytic markers | ||||
| LDH [IU/L] | 190
|
688·50 [534·50–997·50] | 520·50 [377·00–908·00] | 0·43 [−0·28–1·14] 0·234 |
| Indirect bilirubin [μmol/L] | 248
|
49·62 [24·00–83·10] | 30·16 [15·83–56·60] | 1·005 [0·999–1·012] 0·123 |
| Hemoglobin oxygen saturation | ||||
| SpO2 (%) | 217
|
96 [94·5–98·0] | 98 [97·0–100·0] | 0·72 [0·63–0·83] <0·001 |
| Hepcidin | ||||
| Hepcidin ng/mL | 255 | 2·00 [0·64–6·16] | 4·36 [1·50–9·72] | 0·74 [0·60–0·90] 0·003 |
| Hepcidin <5·5 ng/mL | 95 (73·1%) | 69 (55·2%) | 2·20 [1·23–3·93] 0·007 | |
| Hepcidin/Ferritin ratio | 253 | 0.02 (0.01–0.03) | 0.03 (0.01–0.06) | 0.71 (0.57–0.89) 0.003 |
| Hepcidin/Tranferrin saturation ratio | 250 | 0.07 (0.03–0.17) | 0.15 (0.07–0.46) | 0.72 (0.58–0.89) 0.003 |
| α-thalassaemia 3·7 Deletion | 238 | |||
| Wild Type (αα/ αα) | 93 | 59 (49%) | 34 (29%) | |
| 1 Deletion (−α/ αα) | 96 | 48 (40%) | 48 (41%) | 0·58 [0·27–1·23] 0·155 |
| 2 Deletions (−α/− α) | 49 | 13 (11%) | 36 (31%) | 0·21 [0·07–0·58] 0·003 |
| G6PD deficiency | 216 | |||
| No deficiency | 171 | 85 (77%) | 86 (81%) | |
| Female heterozygous | 14 | 8 (7%) | 6 (6%) | 1.35 [0·39–4·62] 0·634 |
| Male and female homozygous | 31 | 17 (15%) | 14 (13%) | 1.22 [0·43–3·53] 0·702 |
| Fetal hemoglobin (%) | 228 | 4 [1·7–5·2] | 6·7 [4·1–9·7] | 0·74 [0·66–0·84] <0·001 |
Continuous variables are presented as medians with interquartile range in brackets. Binary or categorical variables are presented as the numerator and percentages in brackets. Variables chosen to transform using fractional polynomials fulfilled criteria of non-linearity. Normal ranges are as per international standards except for the following which are either for factors not universally harmonized or are specific to the Tanzanian child population: WBC 109/L (1–5 years 3·7–13·2, 5–13 years 3·7–9·1, 13–18 years (3·2–10·3); erythropoietin 3·1–16·5 IU/L. [33, 34] indicates variable fulfilling criteria for imputation, descriptive statistics reported for original dataset ¶ indicates first-degree fractional polynomial power of 0. a Cut-offs for MCV (fL) were MCV < 75 if age 1–3 years, MCV < 79 if age 3–5 years, MCV < 80 if age 6–11 years, MCV < 82 if age 11-14 years, MCV 15–74 if age 15–74 years [7].