Iron deficiency anemia laboratory findings: Difference between revisions

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{{Iron deficiency anemia}}
{{Iron deficiency anemia}}
 
{{CMG}}; '''Associate Editor(s)-In-Chief:''' [[Priyamvada Singh|Priyamvada Singh, M.D.]] [mailto:psingh13579@gmail.com]
{{CMG}}


==Overview==
==Overview==
Iron status can be assessed through several laboratory tests. Since, each test assesses a different aspect of iron metabolism, results of one test may not always agree with results of other tests. Hematological tests based on characteristics of red blood cells (i.e., Hb concentration, [[hematocrit]], [[mean cell volume]], and [[red blood cell]] distribution width) are generally more available and less expensive than are biochemical tests. Biochemical tests (i.e., erythrocyte protoporphyrin concentration, serum [[ferritin]] concentration, and [[transferrin]] saturation), however, detect earlier changes in iron status.
Iron studies are conducted if [[microcytic]] [[hypochromic]] [[anemia]] is found on [[complete blood count]] and peripheral blood film. Iron studies are helpful in making the diagnosis of iron deficiency anemia, with serum [[ferritin]] levels being the most widely used test.
 
==Laboratory Findings==
==Laboratory Findings==
===General facts===
* Complete blood count- Hb <10.5mg/dl and MCV <95fL<ref name="pmid26637694">{{cite journal| author=Camaschella C| title=Iron deficiency: new insights into diagnosis and treatment. | journal=Hematology Am Soc Hematol Educ Program | year= 2015 | volume= 2015 | issue=  | pages= 8-13 | pmid=26637694 | doi=10.1182/asheducation-2015.1.8 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=26637694  }} </ref><ref name="pmid25946282">{{cite journal| author=Camaschella C| title=Iron-deficiency anemia. | journal=N Engl J Med | year= 2015 | volume= 372 | issue= 19 | pages= 1832-43 | pmid=25946282 | doi=10.1056/NEJMra1401038 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=25946282  }} </ref><ref name="pmid26314490">{{cite journal| author=Lopez A, Cacoub P, Macdougall IC, Peyrin-Biroulet L| title=Iron deficiency anaemia. | journal=Lancet | year= 2016 | volume= 387 | issue= 10021 | pages= 907-16 | pmid=26314490 | doi=10.1016/S0140-6736(15)60865-0 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=26314490  }} </ref><ref name="pmid22288902">{{cite journal| author=Khadem G, Scott IA, Klein K| title=Evaluation of iron deficiency anaemia in tertiary hospital settings: room for improvement? | journal=Intern Med J | year= 2012 | volume= 42 | issue= 6 | pages= 658-64 | pmid=22288902 | doi=10.1111/j.1445-5994.2012.02724.x | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=22288902  }} </ref>.
* Although all of these tests can be used to assess iron status, no single test is accepted for diagnosing iron deficiency.
* Microcytic and hypochromic anemia on peripheral blood film.
* Lack of standardization among the tests and a paucity of laboratory proficiency testing limit comparison of results between laboratories.
* Red cell distribution width increased.
* Laboratory proficiency testing is currently available for measuring Hb concentration, [[hematocrit]], [[red blood cell]] count, serum [[ferritin]] concentration, and serum iron concentration, total iron-binding capacity, erthrocyte protoporphryin concentration.
* [[Reticulocyte]] count is low.
* Regardless of whether test standardization and proficiency testing become routine, better understanding among health-care providers about the strengths and limitations of each test is necessary to improve screening for and diagnosis of iron-deficiency anemia, especially because the results from all of these tests can be affected by factors other than iron status.
* Iron studies:
* Because of their low cost and the ease and rapidity in performing them, the tests most commonly used to screen for iron deficiency are Hb concentration and hematocrit (Hct).
** Iron stain (prussian blue staining) of erythroid precursors (sideroblasts) on marrow spicules shows lack of stainable iron in erythroid precursors.
* These measures reflect the amount of functional iron in the body.
** Serum [[ferritin]] levels < 30ng/ml, and serum ferritin <41 ng/mL in a patient with anemia and comorbidities (chronic diseases/inflammation)
* The concentration of the iron-containing protein Hb in circulating red blood cells is the more direct and sensitive measure.
** Serum iron '''<60 mcg/dL.'''
* Hct indicates the proportion of whole blood occupied by the red blood cells; it falls only after the Hb concentration falls.
** Total iron binding capacity/ serum transferrin- TIBC is calculated by multiplying serum [[transferrin]] by 1.389. It is increased in iron deficiency anemia and decreased in anemia of chronic disease. TIBC>'''350 to 400 mcg/dL''' is diagnostic of iron deficiency.
* Since, changes in Hb concentration and Hct occur only at the late stages of iron deficiency, both tests are late indicators of iron deficiency
** [[Transferrin]] saturation (TSAT) is the ratio of serum iron to TIBC: (serum iron  ÷  TIBC  x  100). It is <15% in iron deficiency (normal is 25-40%).
 
* Elevated [[Red blood cell|erythrocyte]] (RBC) zinc [[protoporphyrin]] (eg, >80 mcg/dL).
Anemia will be diagnosed on the basis of suggestive symptoms, or found on the basis of routine testing, which includes a [[complete blood count]] (CBC). A sufficiently low [[hemoglobin]] or [[hematocrit]] value is diagnostic of anemia, and further studies will be undertaken to determine its cause. One of the first abnormal values to be noted on a CBC will be a high [[red blood cell distribution width]] (RDW), reflecting a varied size distribution of [[erythrocytes|red blood cells]]. A low [[Mean corpuscular volume|MCV]], [[Mean corpuscular hemoglobin|MCH]] or [[Mean corpuscular hemoglobin concentration|MCHC]], and the appearance of the RBCs on visual examination of a [[peripheral blood smear]] will narrow the diagnosis to a ''microcytic anaemia''. Microcytic anemia can also be the result of malabsorption phenomena associated with [[gluten-sensitive enteropathy associated conditions#Anemia| gluten-sensitive enteropathy]]/[[coeliac disease]].  
* Decreased iron stain on eryhtroid precursors.
 
The diagnosis of iron deficiency anemia will be suggested by appropriate history (e.g., anemia in a menstruating woman), and by such diagnostic tests as a low serum [[ferritin]], a low serum [[iron]] level, an elevated serum [[transferrin]] and a high [[total iron binding capacity]] (TIBC). [[Serum]] ferritin is the most [[sensitivity (tests)|sensitive]] lab test for [[iron deficiency anemia]].<ref>{{cite journal | author = Guyatt G, Patterson C, Ali M, Singer J, Levine M, Turpie I, Meyer R | title = Diagnosis of iron-deficiency anemia in the elderly. | journal = Am J Med | volume = 88 | issue = 3 | pages = 205-9 | year = 1990 | id = PMID 2178409}}</ref>


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Iron deficient anemia and Thalassemia Minor present with many of the same lab results.  It is very important not to treat a patient with Thalassemia with an iron supplement as this can lead to hemochromatosis (accumulation of iron in the liver)  A hemoglobin electrophoresis would provide useful evidence in distinguishing these two conditions, along with iron studies.
* A [[full blood count]] would likely reveal [[microcytic anemia]] <ref> {{cite book
  | last = Longmore
  | first = Murray
  | coauthors = Ian B. Wilkinson, Supaj Rajagoplan
  | title = Oxford Handbook of Clinical Medicine, 6th Edn
  | publisher = Oxford University Press
  | date = 2004
  | pages = pp. 626-628
  | isbn = 0-19-852558-3 }} </ref>
* Low serum [[ferritin]]
* Low [[serum iron]]
* High [[TIBC]] (total iron binding capacity)
* It is possible that the [[fecal occult blood]] test might be positive, if iron deficiency is the result of [[gastrointestinal bleeding]].
As always, laboratory values have to be interpreted with the lab's [[reference values]] in mind and considering all aspects of the individual clinical situation.
Serum ferritin can be elevated in inflammatory conditions and so a normal serum ferritin may not always exclude iron deficiency.


==References==
==References==
{{Reflist|2}}
{{reflist|2}}
 
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[[Category:Hematology]]
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Priyamvada Singh, M.D. [2]

Overview

Iron studies are conducted if microcytic hypochromic anemia is found on complete blood count and peripheral blood film. Iron studies are helpful in making the diagnosis of iron deficiency anemia, with serum ferritin levels being the most widely used test.

Laboratory Findings

  • Complete blood count- Hb <10.5mg/dl and MCV <95fL[1][2][3][4].
  • Microcytic and hypochromic anemia on peripheral blood film.
  • Red cell distribution width increased.
  • Reticulocyte count is low.
  • Iron studies:
    • Iron stain (prussian blue staining) of erythroid precursors (sideroblasts) on marrow spicules shows lack of stainable iron in erythroid precursors.
    • Serum ferritin levels < 30ng/ml, and serum ferritin <41 ng/mL in a patient with anemia and comorbidities (chronic diseases/inflammation)
    • Serum iron <60 mcg/dL.
    • Total iron binding capacity/ serum transferrin- TIBC is calculated by multiplying serum transferrin by 1.389. It is increased in iron deficiency anemia and decreased in anemia of chronic disease. TIBC>350 to 400 mcg/dL is diagnostic of iron deficiency.
    • Transferrin saturation (TSAT) is the ratio of serum iron to TIBC: (serum iron  ÷  TIBC  x  100). It is <15% in iron deficiency (normal is 25-40%).
  • Elevated erythrocyte (RBC) zinc protoporphyrin (eg, >80 mcg/dL).
  • Decreased iron stain on eryhtroid precursors.
Change in lab values in iron deficiency anemia
Change Parameter
Decrease ferritin, hemoglobin, MCV
Increase TIBC, transferrin, RDW

References

  1. ↑ Camaschella C (2015). "Iron deficiency: new insights into diagnosis and treatment". Hematology Am Soc Hematol Educ Program. 2015: 8–13. doi:10.1182/asheducation-2015.1.8. PMID 26637694.
  2. ↑ Camaschella C (2015). "Iron-deficiency anemia". N Engl J Med. 372 (19): 1832–43. doi:10.1056/NEJMra1401038. PMID 25946282.
  3. ↑ Lopez A, Cacoub P, Macdougall IC, Peyrin-Biroulet L (2016). "Iron deficiency anaemia". Lancet. 387 (10021): 907–16. doi:10.1016/S0140-6736(15)60865-0. PMID 26314490.
  4. ↑ Khadem G, Scott IA, Klein K (2012). "Evaluation of iron deficiency anaemia in tertiary hospital settings: room for improvement?". Intern Med J. 42 (6): 658–64. doi:10.1111/j.1445-5994.2012.02724.x. PMID 22288902.

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