The “Blue Marrow”: when inappropriateness in laboratory medicine leads to unnecessary invasive procedures—a case report

Background: In vitamin B12 deficiency, bone marrow suppression is common and can potentially affect all cell lines, but megaloblastic anemia is the most frequent. The causes of vitamin B12 deficiency are numerous, such as decreased ileal absorption, decreased intrinsic factor that is necessary for a correct absorption of this vitamin, inadequate intake, and prolonged medication use. Laboratory medicine has become a fundamental discipline in the diagnostic process and in medical care. The issue of appropriateness plays an increasing role in laboratory medicine, and in this regard, the concept of appropriateness in laboratory medicine has evolved in years. Case Description: An adult male presented to the emergency department of our hospital for marked asthenia for about a week, with a weight loss of approximately six kilograms in the last month and repeated episodes of nausea and vomiting. On admission, blood analysis showed severe anemia, with a hemoglobin of 39 g/L (3.9 g/dL), leukopenia (1.88×103/µL) and thrombocytopenia (26×103/µL). The suspicion of a possible acute hematological disease has raised. A bone marrow aspirate is performed, and the microscopic evaluation showed a hypercellular marrow with erythropoietic hyperplasia, with megaloblasts instead of normoblasts without evidence of acute hematological neoplasms. This picture is typical in case of severe deficit of vitamin B12. The final diagnosis was made of pernicious anemia and vitamin B12 supplementation was started. Note that in the following days, the patient has also claimed to be a strict vegetarian. Conclusions: This case report is a very good example of inappropriateness in laboratory medicine for the failure to request the appropriate test for the right patient at the right time, specifically the measurement.