Evaluation of the Efficacy of Flow-Cytometry in the Work-up of Leukopenia: An Institutional Retrospective Analysis

Flow-cytometry is an advantageous test which was first used in the 1950s and has now expanded to include the various fields of Immunology, Hematology, Oncology, Blood-banking and Genetic disorders. However, it is a relatively expensive and time-consuming test. We noticed that in our institution, many of the referrals for leukopenia were being evaluated by the flow-cytometry test. Hence, we aimed to review the utility and efficacy of this test with a focus on highlighting the areas where it can be avoided.

We designed a retrospective study to examine data from all leukopenia/neutropenia referrals made to our center in the timespan of 1993-2018. The study included all patients aged >18 years; excluded any patients who were not directly seen in the hematology clinic by the time of data collection. The study protocol was approved by our Institutional review board (IRB). We received de-identified data, reviewed those charts, categorized them based on their reason for referral; presence of underlying cardiovascular disease, liver disease, rheumatological disease, hepatomegaly, splenomegaly. We then looked at what percentage of these patients received flow-cytometry analysis and how many of them turned out to be positive for hematologic malignancies.We further conducted statistical analysis using SAS to examine these trends.

After filtering out patients based on exclusion criteria we ended up with 152 patients in our study. The reason for referral was varied and included bi-cytopenias (6.5%), concern for malignancy(1.31%), aplastic anemia (2.63%), pancytopenia (3.2%) with the majority being for neutropenia (44.7%). We found co-existing cardiovascular disease in 4.6% of patients which included congenital heart disease (28.5%), atrial fibrillation (42%), coronary artery disease (28.5%), congestive heart failure (14.2%) and supraventricular tachycardia (14.2%). Co-existing liver disease was seen in 15% of the patients and was categorized as Hepatitis C infection (47.3%), cirrhosis of the liver (36.8%) and metastatic neoplasm to the liver (5.26%). Rheumatological disease was seen in 13% of patients with the causes being rheumatoid arthritis (47%), Systemic lupus erythematosus (30%), Myasthenia gravis (5.8%), Felty's syndrome (5.8%), and Sarcoidosis (5.8%).Hepatomegaly was seen in 3% of patients and splenomegaly was seen in 7.8% of patients. Flow-cytometry analysis was done in 36% of patients and not done in 64% of patients. It was positive in only 3.9% of patients which resulted in diagnosis of Acute myeloid leukemia (0.65%), Large granular leukemia(0.65%), Myelodysplastic syndrome(0.65%) and Natural-Killer cell lymphoproliferative disorder (0.65%). Further work up revealed elevated IgG, monoclonal gammopathy, aplastic anemia in 1.97% of patients.

The overall predominant causes of leukopenia were benign ethnic neutropenia (17%), medication related (12.5%), autoimmune (5.2%), malignancy (3.9%), viral (4.6%), toxic (2.6%) causes. The medications which caused neutropenia were antibiotic and antifungal (1.31%), anti-seizure (3.2%), immunosuppressant and immunomodulatory (3.2%), psychiatric (2.6%).During evaluation of leukopenia, a thorough history can rule out toxic and medication-related causes. The review of old medical records and laboratory results can lead to the diagnosis of chronic benign and congenital leukopenia which can avert unwarranted testing. Abstinence from alcohol may lead to reversal of the neutropenia if alcohol is the toxin responsible. Viral testing for HIV and hepatitis should be performed. Evaluation for autoimmune causes is much needed. Since the overall positivity of flow-cytometry was very low in our analysis (3.9%), we propose that such thorough preliminary evaluation can avoid the need for many of these tests.

The data showed that leukopenia referrals come with a wide range of underlying causes including congenital disorders (benign ethnic, familial, congenital neutropenia) and acquired disorders (infection, toxins, medications, nutritional, rheumatological, autoimmune, idiopathic, hematologic malignancies). Peripheral blood flow-cytometry although sensitive for detecting some hematologic malignancies, is unnecessary in the majority of cases. Hence, we highlight here the varied benign causes of neutropenia and quantify them as seen in a tertiary referral center to enable decisions on the judicious use of this test.

No relevant conflicts of interest to declare.