REF-1414 · Kaufmann et al., 2021 · Scandinavian Journal of Medicine & Science in Sports · Paper · PubMed

Is my ferritin valid the week after a marathon?

Not as a store reading: in 15 runners ferritin rose with CRP after a marathon and a 130-km ultra and was still raised at a follow-up within 5 days. Test later, rested (practice).

Main caveat: Abstract only; the full text was not open.
limited, mixed evidenceMeasured on trained athletes

Kaufmann and colleagues, a cardiology group in Vienna, measured inflammation and iron markers in 15 well-trained non-professional endurance athletes (14 men, 1 woman) who ran both a 130-km ultra-marathon and a standard marathon, sampling before, immediately after and within 5 days after each run.

Leucocytes, neutrophils, monocytes and CRP rose significantly after both races, CRP more after the ultra (18.15 ± 12.41 vs 5.58 ± 9.65 mg/L immediately after; 15.67 ± 16.97 vs 7.19 ± 7.75 mg/L at follow-up).

Ferritin also rose significantly after both races and "remained high at follow-up", and was higher after the ultra both immediately (111.5 ± 103.2 vs 84.8 ± 86.3) and at follow-up (102.7 ± 79.5 vs 74.6 ± 65.6). Serum iron and transferrin saturation moved in opposite directions — up after the marathon, down after the ultra.

The authors conclude that inflammation is greater after an ultra and that iron markers respond differently with distance. Our reading: the first measured size and duration of the post-race ferritin rise in the base; it grounds the rule not to read a ferritin taken in the days after a long race as a store measurement, which PHYS-36 and PHYS-44 state as mechanism only.

Protocol

Participants: n = 15 (14 men, 1 woman), well-trained, non-professional endurance athletes.
Races: a 130-km ultra-marathon and a 42.195-km marathon, both run by every participant (order and interval not given in the abstract).
Sampling: before, immediately after, and within 5 days after each race.
Markers: leucocytes, neutrophil granulocytes, monocytes, CRP; ferritin, serum iron, transferrin saturation (others, such as hepcidin, are not named in the abstract).
Funding and interests (PubMed): the Association for the Promotion of Research on Arteriosclerosis, Thrombosis, and Vascular Biology (ATVB) and the Ludwig Boltzmann Cluster for Cardiovascular Research; no conflict-of-interest statement in the abstract record.

Key Results

MarkerUltra-marathonMarathonp
CRP immediately after (mg/L)18.15 ± 12.415.58 ± 9.65< .001
CRP at follow-up (mg/L)15.67 ± 16.977.19 ± 7.75.045
Ferritin immediately after111.5 ± 103.284.8 ± 86.3.001
Ferritin at follow-up (within 5 days)102.7 ± 79.574.6 ± 65.6.001
Ferritin units are not given in the abstract (µg/L is the usual unit; our reading). Pre-race values are not in the abstract.
Within each race: ferritin "increased significantly after both races and remained high at follow-up"; inflammatory cells and CRP rose significantly after both.
Serum iron and transferrin saturation: increased after the marathon, decreased after the ultra, giving a significant absolute difference between races.

Mechanisms

Measured: an acute-phase response (CRP, white cells) after both races, larger after the ultra, with ferritin rising alongside and still raised days later.
Authors' interpretation: a higher degree of inflammation after the ultra than after the marathon; iron-homeostasis markers respond differently with running distance.
Inference: ferritin is an acute-phase protein, so after a long race a value can look normal or high while stores are low (REF-1411; REF-1410); the large SDs (ferritin ±103 after the ultra) show wide differences in ferritin between runners; how much each runner's value rose is not given in the abstract.
Inference: the size of the confound depends on the session. REF-1410 cites studies in which ferritin stayed normal or rose 27% and returned within a day, depending on the duration and intensity of the activity, but after ultramarathons doubled and returned to baseline only after 6 days; this study measured only races.This study measured races only; REF-1410 also names training sessions among the acute-phase reactions to exclude, so the size of the confound after an ordinary session is not measured in the base.

Practical Application

Is my ferritin valid the week after a marathon? Not as a store reading: in 15 runners ferritin rose with CRP after a marathon and a 130-km ultra and was still raised at a follow-up within 5 days. Test later, rested (practice).
When to draw blood (practice built on this study): not in the days after a marathon or longer race, nor during or soon after an illness; the measured window is "within 5 days", the one-week wait in the card is practice proposed here (no base line sets it yet), not a finding. Ask for CRP alongside (REF-1410).
Transferrin saturation after a race is unreliable too: it went up after the marathon and down after the ultra.
What this gives the base: a measured size for the inflammation caution in PHYS-36 and PHYS-44, and the limit that it is shown for long races, not for an ordinary training day.
Not shown: how long the rise lasts beyond 5 days, the response in women, after shorter races or training blocks, or whether stores themselves changed.

Limitations

Abstract only; the full text was not open.
Small and male: 15 runners, one woman.
One follow-up sample "within 5 days"; the exact day, baseline values, race order and the interval between races are not in the abstract; ferritin units not given.
Races only: no ordinary training session, no shorter race, no illness comparison.
Funding and interests: two cardiovascular research bodies per PubMed; no conflict statement in the record.
How this entry was checked and changed
Why this level

(from the abstract) — a small paired observational cohort (rubric B) held at B- because key methods are missing from the abstract (the follow-up day, the race order and interval, baseline values and ferritin units); 14 of 15 are men and the outcomes are blood markers