European Journal of Cardiovascular Medicine

Macrocytosis, characterized by abnormally large red blood cells (RBCs), is indicated by elevated Mean Corpuscular Volume (MCV) in the complete blood count (CBC). Often, high MCV values coincide with increased Mean Corpuscular Haemoglobin (MCH), serving as an indicator of macrocytosis [1]. While macrocytosis may not always necessitate immediate medical intervention, understanding its implications, particularly in the development of macrocytic anaemia and its diverse underlying pathologies involving extra-hematologic organ systems, is crucial for clinicians [2].

Differentiating the causes of macrocytic anaemias aids in tailored management approaches, typically categorized into megaloblastic and non-megaloblastic types. Megaloblastic anaemias, identified by distinct morphological features on peripheral blood smear examination, primarily stem from deficiencies in vitamin B12 and folate, essential for nuclear maturation [3,4]. Evaluation of plasma or serum levels of these vitamins, along with red cell folate, is imperative in diagnosing megaloblastic anaemia as deficiencies impair DNA synthesis, leading to ineffective erythropoiesis [5].

Vitamin B12 deficiency, often indicative of malabsorptive diseases, manifests with various clinical implications, including compromised red blood cell synthesis, impacting oxygen transport [6]. Similarly, folate insufficiency, influenced by factors such as dietary intake and absorption disorders, underscores the importance of proper nutrient uptake and absorption mechanisms [7,8]. Moreover, alcoholism, certain medications, and physiological conditions can exacerbate folate deficiencies, necessitating comprehensive assessment in clinical practice [9,10].

Beyond megaloblastic etiologist, non-megaloblastic causes of macrocytosis encompass diverse pathologies, including liver diseases and alcohol consumption. Liver diseases, characterized by cholesterol deposition on RBC membranes, contribute to macrocytosis, while chronic alcohol consumption impairs hematopoiesis, resulting in enlarged and structurally abnormal erythrocytes [11].

This study aims to delineate macrocytic anaemia into megaloblastic and non-megaloblastic subtypes through comprehensive haematological and biochemical analyses. Furthermore, it seeks to evaluate distinctive haematological features among different etiologist in macrocytic patients.

A prospective observational study was conducted from January 2021 to November 2021 at the Department of Biochemistry, MKCG Medical College and Hospital, Berhampur, Odisha, India. The study enrolled a total of 350 adult patients presenting with a Mean Corpuscular Volume (MCV) of equal to or greater than 100 fl. Excluded from the study were newborns, pregnant women, individuals with reticulocytosis, and cases of spurious macrocytosis. Ethical clearance was obtained from the institutional ethics review board prior to commencing the study.

All samples received for analysis, including complete blood count (CBC), peripheral smear, and selected bone marrow and biochemical parameters, were included in the study after thorough screening. Samples from neonates or children, haemolyzed samples, and those with interference in assay were excluded. Data for analysis were obtained from the Laboratory Information System (LIS) and medical records after appropriate clearance from the Institutional Ethical Review Board (IERB).

A comprehensive medical history was obtained from all participants, focusing on dietary habits, medication usage, and alcohol consumption. Alcoholism was defined based on sustained and regular excessive drinking, alcohol tolerance, and withdrawal symptoms.

Serum levels of Vitamin B12 (Cobalamin) and folic acid, along with liver function tests, were assessed using fasting blood samples. Vitamin B12 and folic acid assays were performed using the ADVIA CENTAUR XP immunoassay system, while liver function tests were conducted using the DIRUI CS-400 Auto-biochemistry analyser.

Detailed evaluation of red cell parameters and peripheral smear findings was carried out for all cases. Based on identified etiological factors, patients were categorized into megaloblastic and non-megaloblastic groups. Bone marrow aspiration was performed in selected cases for further evaluation.

Data collected, including patient details and biochemical parameters, were entered into an Excel spreadsheet. Statistical analysis was performed using the R software. Quantitative variables were analysed using the chi-square test and t-test to assess differences between groups.

A total of 350 patients were enrolled in the study, comprising 281 males and 69 females, with mean ages of 48.49 ± 14.09 years for males and 49.05 ± 16.61 years for females. Among the patients, 162 (46.29%) were diagnosed with megaloblastic anaemia, while 188 (53.71%) presented with non-megaloblastic macrocytosis.

Table 1 Age and Gender distribution of study participants

When analysing haematological and biochemical parameters between the two groups, significant differences were observed in several variables. Notably, patients with megaloblastic anaemia exhibited lower levels of red blood cells (RBC), white blood cells (WBC), haemoglobin (HB), packed cell volume (PCV), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin concentration (MCHC), and elevated red cell distribution width (RDW) compared to those with non-megaloblastic macrocytosis (p < 0.001 for RDW, p < 0.005 for MCH, MCHC, p < 0.01 for HB, PCV, p < 0.05 for RBC, WBC, MCV). Conversely, levels of folic acid and vitamin B12 were significantly lower in patients with megaloblastic anaemia compared to those with non-megaloblastic macrocytosis (p < 0.001). There were no significant differences in renal function tests (RFT), liver function tests (LFT), and other biochemical parameters between the two groups.

Table 2 Haematological and Biochemical parameters among study participants

Further analysis of non-megaloblastic macrocytosis cases revealed various underlying conditions contributing to the pathology. Among these cases, excessive alcohol intake was the most prevalent etiology, accounting for 64.29% (225 cases) of non-megaloblastic macrocytosis. Other notable causes included patients receiving dialysis (8.86%), ulcerative colitis (10.57%), Crohn's disease (3.71%), anti-epileptic drug use (7.43%), and haemolytic anaemia (4.57%).

Table 3 Non megaloblastic macrocytosis, and their clinical correlation.

Overall, the study highlights the diverse etiologist and distinct haematological and biochemical profiles associated with megaloblastic and non-megaloblastic macrocytosis, emphasizing the importance of comprehensive evaluation for accurate diagnosis and management strategies.

Our study underscores the importance of evaluating macrocytosis even in the absence of anaemia, as it may serve as an initial indicator of underlying pathologies. Thorough assessment of medical history, including alcohol and drug intake, coupled with detailed evaluation of red cell parameters and peripheral smear, aids in establishing a provisional diagnosis, particularly in resource-limited settings. Various studies have reported numerous causes of macrocytosis within different populations. Savage et al. highlighted pharmacological therapy and alcohol addiction as the most common causes, with Vitamin B12/folate deficiency being less frequent [14]. Similarly, Keenan et al. identified haematological diseases and alcohol consumption as predominant causes [15]. Mahmoud et al. associated macrocytosis with a higher risk of haematological disorders and malignancies among older adults [16].

In our study, we observed that a substantial proportion of patients with macrocytosis did not present with anaemia, indicating diverse underlying etiologist. Vitamin B12/folate insufficiency was the most common cause of anaemia among these cases, often co-existing with alcoholism [22]. Notably, isolated macrocytosis without anaemia was observed in a significant number of patients with vitamin B12 insufficiency, highlighting its potential as an early diagnostic marker preceding anaemia [24].

Regarding mean corpuscular volume (MCV), we found that levels exceeded the typical range in cases of both vitamin B12/folate insufficiency and alcoholism, with prolonged alcohol consumption leading to toxic effects on marrow erythroid precursors. The mean red cell distribution width (RDW) was notably higher in megaloblastic cases compared to non-megaloblastic conditions, consistent with previous findings associating elevated RDW with megaloblastic processes [25].

Furthermore, distinctive red cell characteristics, such as macro-ovalocytes and hyper segmented neutrophils, were more frequently observed in megaloblastic macrocytosis compared to non-megaloblastic conditions. However, these features were also present, albeit less frequently, in cases of alcoholism, where predominantly round, uniform macrocytes were observed [31].

Medication-induced macrocytosis was noted in various studies, implicating drugs such as anticonvulsants, folate antagonists, and chemotherapeutics. Notably, HIV patients on reverse transcriptase inhibitor therapy often exhibit macrocytosis without anaemia, serving as a surrogate marker for medication adherence [29].

In conclusion, our study underscores the diverse etiologist and diagnostic challenges associated with macrocytosis. Comprehensive evaluation incorporating medical history, laboratory investigations, and peripheral smear examination is crucial for accurate diagnosis and appropriate management of patients presenting with macrocytosis. Further research is warranted to elucidate the underlying mechanisms and optimize diagnostic strategies for this clinically significant condition.

In conclusion, our study underscores the significance of comprehensive evaluation in diagnosing macrocytosis, even in the absence of anaemia. By delineating megaloblastic and non-megaloblastic subtypes, we identified diverse underlying pathologies, with megaloblastic anaemia primarily associated with vitamin B12 and folate deficiencies, and non-megaloblastic macrocytosis linked to liver diseases and chronic alcohol consumption.

The study's findings highlight the diagnostic challenges posed by macrocytosis and emphasize the importance of peripheral smear examination in identifying characteristic red cell features. Notably, isolated macrocytosis without anaemia, particularly in vitamin B12 insufficiency, suggests its potential as an early diagnostic marker preceding anaemia onset. Furthermore, elevated red cell distribution width (RDW) in megaloblastic cases and the presence of macro-ovalocytes and hyper segmented neutrophils serve as key diagnostic indicators. These insights contribute to a deeper understanding of macrocytosis pathophysiology and inform tailored management strategies.

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