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Hematology is a unique science in that its complexity is readily accessible via the examination of blood and marrow. The ease with which a complete blood count (CBC) may be obtained also leads to frequent observation of values which fall outside the reference range. Such perturbations may be the sign of something as ominous as acute leukemia, or as inconsequential as the common cold. That such changes might generate considerable anxiety, both for patients and providers, is not surprising given the plethora of life-threatening diseases that often manifest classic CBC findings.

This ever-increasing dependence on labs as screening tools generates a seemingly endless supply of “abnormal” results, often triggering hematologic consultation. Electronic medical records (EMRs), as repositories for this ever-growing data, serve as invaluable tools in evaluating the chronicity and trend of such findings.

In this chapter, we outline our approach to dealing with these common queries. The individual epidemiology, pathogenesis, and treatment of such disorders are covered comprehensively and with clarity within their corresponding chapters and are not repeated here. Rather, what we describe is our thought process in approaching such questions and narrowing the broad differential to that which is reasonable and probable.

Acronyms and Abbreviations:

AC, anticoagulation; ACD, anemia of chronic disease; ADAMTS13, a disintegrin and metalloprotease with a thrombospondin type 1 motif member 13; ALC, absolute lymphocyte count; ALL, acute lymphoblastic leukemia; ANC, absolute neutrophil count; APS, antiphospholipid antibody syndrome; BCR-Abl, breakpoint cluster region-Abelson; CBC, complete blood count; CD, clonal designator; CLL, chronic lymphocytic leukemia; CML, chronic myelogenous leukemia; CMML, chronic myelomonocytic leukemia; CNL, chronic neutrophilic leukemia; CRP, C-reactive protein; DIC, disseminated intravascular coagulation; DVT, deep venous thrombosis; EDTA, ethylenediaminetetraacetic acid; EMR, electronic medical record; EPO, erythropoietin; ER, emergency room; ESR, erythrocyte sedimentation rate; ET, essential thrombocythemia; HELLP, hemolysis, elevated liver enzymes, low platelet count; HHT, hereditary hemorrhagic telangiectasia; HIT, heparin-induced thrombocytopenia; HUS, hemolytic uremic syndrome; ITP, immune thrombocytopenia; JAK2, Janus kinase 2; LDH, lactate dehydrogenase; LGL, large granular lymphocytic; LMWH, low-molecular-weight heparin; MCH, mean corpuscular hemoglobin; MCV, mean corpuscular volume; MDS, myelodysplastic syndrome; MGUS, monoclonal gammopathy of undetermined significance; MPN, myeloproliferative neoplasm; MTHFR, methylenetetrahydrofolate reductase; nRBC, nucleated red blood cell; NSAID, nonsteroidal antiinflammatory drug; p50, partial pressure required to achieve 50 percent saturation; PCR, polymerase chain reaction; PE, pulmonary embolism; PFA, platelet function analysis; PMN, polymorphonuclear neutrophil; PNH, paroxysmal nocturnal hemoglobinuria; PT, prothrombin time; PTT, partial thromboplastin time; PV, polycythemia vera; RBC, red blood cell; RIPA, ristocetin-induced platelet aggregation; RT, reptilase time; SPEP, serum protein electrophoresis; TT, thrombin time; TTP, thrombotic thrombocytopenic purpura; UPEP, urine protein electrophoresis; VWD, von Willebrand disease; WBC, white blood cell.


Detection of a low white blood cell (WBC) count is a common reason for hematologic consultation. Clinicians and patients are attentive to early signs of marrow pathology, such as myelodysplastic syndrome (MDS), although such diseases are found only in a minority of referrals. Nevertheless, the severity of potential ...

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