Reviews/Iron Status/Intravenous iron raises haemoglobin faster
Ida · IRON-IDA-03 · v2
Borderline: within 4 points of the Established/Likely boundary, so a re-grade could land either side.
Across several separate trials in pregnant women, kidney-disease patients, cardiac-surgery patients and general anaemia, the haemoglobin level rose more in the early weeks when iron was given by vein rather than by mouth [2][10][11][4]. The one trial built specifically to compare the speed of the rise found the intravenous route worked faster early on, but the two routes ended up at a similar level by the end of treatment [7]. So the panel treated the claim as being about speed, not about who ends up healthier: the early lead is real but often temporary. It also noted that many trials let both patients and doctors know which treatment was given, and that a couple of trials added a separate blood-boosting drug that muddies the comparison. These issues are why the panel supported the claim but did not treat it as fully settled.
Multiple independent randomised trials report a larger early haemoglobin increment with intravenous iron than with oral iron: greater mean rise at Weeks 6, 12 and 18 in pregnancy [2], a higher mean increase at 12 weeks (4.3 ± 1.1 vs 2.7 ± 1.4 g/dL; p < 0.001) [10], higher Hb at 3 weeks (10.05±0.73 versus 9.59±0.73 gm/dl; p<0.001) [11], and higher mean Hb at 4 weeks after cardiac surgery (12.0 ± 1.1 g/dL vs 11.4 ± 1.3 g/dL; P = .013) [4]. The trial designed to test kinetics directly found IV "produced a more rapid Hb increase" that was significant at the first month but where "such difference disappeared at the end of treatment" [7]. Counter-evidence bears on final anaemia state rather than speed: no difference in anaemia at 36 weeks [3] and no improvement in attaining a nonanemic state [1]. The contested point: The division is between speed and durability: the early haemoglobin advantage for IV is consistent, but [7] shows it converges by end of treatment and [3] finds no difference in anaemia at 36 weeks. The evidence therefore supports "faster" but does not support a superior final haemoglobin state.
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One reviewer's only job is to attack the finding. The challenges below were weighed before the grade was set.
The advantage is transient, not durable: [7] states the IV-vs-oral difference 'disappeared at the end of treatment' and [3] found no anaemia difference at 36 weeks. 'Faster' is supported but must not be read as a superior final Hb.
Confounding by co-intervention: [6] gives the IV arm darbepoetin (an ESA) and [8] gives both arms darbepoetin, so neither cleanly isolates the effect of the IV route on Hb kinetics.
Where it remains uncertain. The advantage is transient: [7] reports the difference "disappeared at the end of treatment" and [3] found no anaemia difference at 36 weeks.
Aleatory
The kinetics-relevant signal in [9] rests on 23 analysed patients and the trial was stopped early; [5] was stopped for futility, leaving noisy estimates.
The load-bearing papers from a corpus of 11, each classified by what it does to the claim. Every DOI is taken from the corpus the claim was graded on.
Serial multi-timepoint evidence of a consistently greater and earlier Hb rise with IV.
“The mean Hb increase was significantly greater with IV iron versus oral iron at Weeks 6 (0.4 versus - 0.2 g/dL; p < 0.001), 12 (0.5 versus 0.1 g/dL; p < 0.001), and 18 (0.8 versus 0.5 g/dL; p = 0.01).”
Panel auditInternal validity: medium · scope of inference: Pregnant women 14-21 weeks with persistent iron deficiency after routine oral iron.Key limitations: open-label · single centre · population had already failed oral iron
Counter-evidence: any early advantage need not translate to a durable difference in final anaemia state.
“No significant difference was found in anaemia at 36 weeks (299 [58%] of 517 in the intravenous group vs 305 [61%] of 503 in the oral group; risk ratio 0·95, 95% CI 0·85-1·06; p=0·36)”
Panel auditInternal validity: high · scope of inference: Pregnant women 20-32 weeks with Hb <10 g/dL in Nigeria.Key limitations: open-label · endpoint is anaemia prevalence, not Hb velocity · single-dose IV
Higher Hb at 4 weeks in a non-pregnancy (cardiac surgery) setting, extending generalisability.
“Mean hemoglobin levels (± standard deviation) were higher in the IV iron group (12.0 ± 1.1 g/dL vs 11.4 ± 1.3 g/dL; P = .013).”
Panel auditInternal validity: medium · scope of inference: Post-cardiac-surgery patients with moderate anaemia (Hb 8-11 g/dL).Key limitations: single 4-week time point only · secondary endpoint · single centre · null primary outcome
The abstract reports proportions achieving a nonanaemic state (RR 1.05 and 1.06, not improved) but gives no interim haemoglobin time-course, so which arm raised Hb faster cannot be determined.
Panel auditInternal validity: high · scope of inference: Second-trimester pregnant women with moderate iron deficiency anaemia (Hb 7.0-9.9 g/dL) in India, single-dose IV vs twice-daily oral iron.Key limitations: endpoint is nonanaemic proportion, not Hb velocity · single-dose IV vs continuous oral dosing · semiblind
4 of 11 papers shown. The full review lists all of them, with the panel’s arbitration →
Claims are graded at each quarterly release, and re-graded between releases only when a pivotal trial lands. Every change is a new version of the claim.
Consistent, directly-measured early Hb superiority for IV supports the speed claim, but transience, open-label bias and co-intervention confounding cap confidence short of Established.
Release 2026-q4 re-graded every claim from its corpus under protocol v0.19. An earlier release's grade is shown for the record; it came from an earlier protocol and is not a movement.
Assumptions that carry weight but are not themselves established.
The panel records the gap that would most move the claim, and the study that would close it.
Blinded head-to-head against standard oral ferrous salts. Every kinetics-relevant trial is open-label ([2],[3],[5],[9]) or uses high-bioavailability oral formulations ([7],[8]), so the speed estimate may be inflated or formulation-specific. The panel rates this the highest-importance open gap for the claim, and names the study design that would close it: A double-blind, double-dummy RCT of IV iron versus standard ferrous sulphate with serial early Hb sampling.
Open question: Does the faster early Hb rise with IV iron persist under blinding, or is it partly an artefact of open-label measurement? Why it is still open: The trials showing the early advantage are open-label or unmasked ([2],[3],[5],[9]) and [9] reports patient crossover.
Priors is a sceptical first reader, not peer review, and not medical advice.
Release 2026-q4 · graded 18 Sep 2026 · protocol v0.19