Ferritin Cutoff Values Affect Diagnosis of Iron Deficiency

Ferritin is the parameter most often used in primary care to diagnose iron deficiency. The cutoff value of ferritin can affect the number of cases diagnosed, however. A study published in JAMA Network Open investigated how different cutoff values affect the diagnosis of iron deficiency.

The study, which included 255,351 adult primary care patients in Switzerland, showed that ferritin cutoff values of 15, 30, and 45 ng/mL were associated with incidences of iron deficiency diagnoses of 10.9, 29.9, and 48.3 cases per 1000 patient-years, respectively. In other words, as the cutoff value increases, the frequency of diagnosis also increases.

“It is a study to take into account, especially because of the number of patients it includes, and it can guide primary care clinical practice. As expected, as the cutoff point increases with respect to ferritin values, the incidence percentages of both iron deficiency and iron-deficiency anemia also increase,” Dr Miguel Turégano-Yedro, a family physician at the Casar de Cáceres Health Center in Casar de Cáceres, Spain, and coordinator of the Hematology Working Group of the Spanish Society of Primary Care Physicians, told Univadis Spain. Ferritin is the most sensitive parameter for diagnosing iron deficiency and iron-deficiency anemia, he added. “When it is necessary to supplement a patient with iron, other parameters are taken into account, such as hemoglobin, to see if there is anemia.”

Ferritin Level

The ferritin level associated with iron deficiency in primary care is usually 15 ng/mL, said Turégano-Yedro. “If we assess patients with a ferritin level of 15 or less than 15, then we know that many cases will be symptomatic (with fatigue, tiredness, or lack of appetite) and, therefore, will need iron treatment. But if the ferritin cutoff value is increased to 30 ng/mL or 45 ng/mL, the incidence will be higher, although in many cases they will be asymptomatic and iron supplementation will not be necessary,” he said.

He also pointed out that he does not consider it necessary to raise the cutoff to 45 ng/mL; however, “establishing the cutoff at 30 ng/mL, in a certain population at risk of iron deficiency or iron-deficiency anemia, may be interesting, for example in women of childbearing age, women with very heavy menstruation, children, frail elderly, people with gastrointestinal bleeding, or those who engage in physical exercise.”

Iron deficiency must be distinguished from anemia. “If the ferritin is below 15 ng/mL, there is iron deficiency, which may or may not be accompanied by symptoms, although usually most patients will have symptoms. Normally, to diagnose a patient with iron-deficiency anemia, on the one hand, they must have low hemoglobin, which indicates anemia, and on the other hand, low ferritin, which indicates iron deficiency.” Taking these parameters into account, the study does have a weakness. “It is striking that a percentage of patients in the study requested ferritin analysis without including hemoglobin, when hemoglobin is part of the basic analysis performed in Spain,” said Turégano-Yedro.

When to Supplement

The study highlights the incidence of nonanemic iron deficiency diagnoses associated with the choice of ferritin cutoff value. However, as Turégano-Yedro explains, the percentage of patients who have iron deficiency but do not have anemia is not very relevant. “In the case of family physicians in Spain, it is not usually taken into account, because if a patient has iron deficiency with or without anemia and is symptomatic, they should be given iron supplements.” What if they do not have a deficiency but do have anemia? “In principle, iron supplementation is not necessary, because that anemia may be due to chronic disorders or it may be hemolytic anemia, so the case should be studied,” Turégano-Yedro concluded.

This story was translated from Univadis Spain, which is part of the Medscape Professional Network, using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.