Potential limitations of diagnostic standard codes to distinguish polycythemia vera and secondary erythrocytosis

Abstract

Red cell overproduction is seen in polycythemia vera (PV), a bone marrow myeloproliferative neoplasm characterized by trilinear cell proliferation (WBC, platelets), as well as in secondary erythrocytosis (SE), a group of heterogeneous disorders characterized by elevated EPO gene transcription. We aimed to verify the concordance of the International Classification of Diseases (ICD) code-based diagnosis of “polycythemia” or “erythrocytosis” with the true clinical diagnosis of these conditions. We retrospectively reviewed the electronic medical records (January 1, 2005, to December 31, 2016) of adult patients with ICD codes of polycythemia and/or erythrocytosis who had testing done for the presence of the JAK2V617F mutation. We verified the accuracy of the ICD code-based diagnoses by meticulous chart review and established whether these patients fulfilled the criteria by the evaluating physician for PV or SE and according to the World Health Organization 2016 diagnostic guidelines. The reliability of ICD coding was calculated using Cohen's kappa. We identified and chart reviewed a total of 578 patient records. Remarkably, 11% of the patients had concurrent diagnosis codes for PV and SE and were unable to be classified appropriately without individual chart review. The ICD code-based diagnostic system led to misidentification in an important fraction of cases. This represents a problem for the detection of PV or SE cases by ICD-based registries and their derived studies. Research based exclusively on ICD codes could have a potential impact on patient care and public health, and limitations must be weighed when research findings are conveyed.

Contribution of lowered hemoglobin threshold value in the diagnosis of polycythemia vera: Comparison of 2016 and 2008 WHO criteria

“…Erythrocytosis, also known as polycythemia, is described as an increase in the concentration of red blood cells (RBC) in the blood, specifically determined by an elevation in hemoglobin or hematocrit values that exceed reference values (according to age and sex) by 2 standard deviations. [1,2] These values are impacted by plasma volume; thus, they are subject to variation with fluid loss due to burns, dehydration and stress. Secondary erythrocytosis is the most common cause of absolute erythrocytosis and is mainly caused by abnormal activation of erythropoietin (EPO) in response to chronically decreased tissue oxygenation, such as chronic obstructive pulmonary disease (COPD), smoking, obstructive sleep apnea syndrome (OSAS), high-altitude habitat or renal disorders.…”

“…[3] Erythrocytosis may also stem from acquired causes, such as medications, kidney transplants, or autonomous EPO production in certain cancers. [1]…”

“…[3] Erythrocytosis may also stem from acquired causes, such as medications, kidney transplants, or autonomous EPO production in certain cancers. [1] Primary erythrocytosis, also known as polycythemia vera (PV), is a member of Philadelphia-negative chronic myeloproliferative neoplasms (MPNs), along with primary myelofibrosis and essential thrombocytosis, characterized by clonal hyperproliferation of erythroid, megakaryocytic and myeloid lineages. [4] PV is associated with changes in the bone marrow typically acquired by Janus kinase (JAK2) somatic mutations.…”