Large Unstained Cell

Overview

Large Unstained Cells (LUC) is a parameter reported by automated hematology analyzers as part of the complete blood count (CBC) with differential. It represents a small population of white blood cells that are larger than typical lymphocytes and do not take up the usual cytochemical stains or do not fit normal analyzer classification algorithms. LUCs commonly include atypical/reactive lymphocytes, blasts, immature granulocytes, monocytes, plasma cells or other abnormal circulating cells. Elevated LUCs can be seen with viral infections, severe bacterial infections, inflammatory or immune responses, and hematologic malignancies (e.g., leukemia, lymphoma). Symptoms prompting testing include fever, unexplained fatigue, swollen lymph nodes, bruising/bleeding, or abnormal CBC results. Normal LUC values vary by analyzer and lab; small numbers are more common in younger adults and may be absent in healthy individuals.

Test Preparation

• No special preparation is required

Why Do I Need This Test

• Included in: Complete Blood Count (CBC) with automated differential.
• Symptoms: fever, malaise, lymphadenopathy, unexplained bruising/bleeding, abnormal CBC.
• Diagnoses/monitoring: reactive infections, immune responses, hematologic malignancies, monitoring of treatment.
• Reasons for abnormal levels: viral infections, severe bacterial infection/sepsis, hematologic cancers, bone marrow stress or recovery, laboratory artifact.
• Biological meaning: elevated LUCs indicate presence of atypical or immature circulating white cells requiring further evaluation.
• Lifestyle/factors: recent infection, medications (steroids, growth factors), smoking, recent transfusion or chemotherapy.
• Family history: hematologic malignancy or inherited marrow disorders increases need for evaluation.

Understanding Test Results

• Values within 0–2% (or up to ~0.05 x10^9/L) are generally considered normal or insignificant.
• Mild elevations (about 2–5% or 0.05–0.2 x10^9/L) commonly reflect reactive/atypical lymphocytes from viral infections (e.g., EBV, CMV), recent vaccination, or inflammatory states.
• Moderate elevations (≈5–10% or 0.2–0.5 x10^9/L) raise concern for more pronounced immune activation or immature granulocytes during severe infection or marrow stress and usually prompt a peripheral smear review.
• Marked elevations (>10% or >0.5 x10^9/L) strongly suggest significant pathology such as acute leukemia, lymphoma with circulating malignant cells, or severe sepsis and require urgent hematology assessment (peripheral smear, flow cytometry, possible bone marrow biopsy).
• Low or zero LUC is common and typically not clinically significant.
• Reference ranges and cutoffs vary by analyzer; any abnormal LUC usually triggers manual smear review and follow-up testing.

FAQs