Fræðigrein

 Background: The purpose of this study was to estimate the value of the transferrin receptor in serum (sTfR) for detecting iron deficiency and compare it with the value of some other blood tests for that purpose.

Material and methods: All patients undergoing bone marrow aspiration in the FSA Hospital, Akureyri, Iceland, in the period 1999 to 2003 were eligible to participate in this prospective study. Included participants were 89. The sensitivity, specificity, efficiency, and Youden index of ferritin, MCV, CHr, sTfR, sTfR-Ferritin-index, the iron saturation of transferrin, and the Thomas-Plot method were calculated. The complete absence of stainable iron in bone marrow was used as the definitive marker of iron depletion.


Results: The best method to detect iron deficiency as estimated by the Youden index was the Thomas-Plot method. This method was very specific in cases without evidence of inflammatory processes (CRP <6 mg/L) and very sensitive in cases with elevated CRP (≥6 mg/L). The sTfR-Ferritin-index came second and sTfR was the best single blood test to detect iron deficiency according to the Youden index. 


Conclusion: The Thomas-Plot method and the sTfR-Ferritin-index proved to be the most reliable blood tests to diagnose iron deficiency. These parameters can eliminate the need of using bone marrow aspirate to diagnose iron defieciency in some cases.

Figure 1.
Thomas-Plot. Classification of iron replete and iron deplete states by the results of CHr, sTfR-ferritin index, and CRP according to C. Thomas and L. Thomas.

Figure 2.
Distribution of iron stores estimated by microscopy.

Figure 3.
Average sTfR and 95% confidence limits for every stage of iron stores in bone marrow. Horizontal lines represent reference limits. Statistically significant difference (p <0,05) is between stage 0 and every other stage of iron stores and between stage 1 and stage 3. No statistically significant difference was found between other stages.

Figure 4.
Average sTfR-Ferritin-index and 95% confidence limits for every stage of iron stores in bone marrow. Horizontal lines represent sTfR-Ferritin-indx 11 and 15. Statistically significant difference (p <0,05) is between all stages of iron stores.

Figure 5.
Average serum ferritin and 95% confidence limits for every stage of iron stores in bone marrow. Statistically significant difference (p <0,05) is between all stages of iron stores.

 

Table I.
Reasons for bone marrow examination and prevalence of iron deficiency in each category.

Table II.
Average and standard deviation of variables covered in the study in iron deficient and iron replete participants and the statistical significance of the difference.

Table III.
* Statistically significant difference (p<0,05) between participants with CRP ≥6 mg/L and CRP <6 mg/L.