A nurse is assessing a 45-year-old client who has been experiencing frequent infections over the past 6 months. Which laboratory finding would most likely indicate compromised immune function?

A WBC count of 2,800/mm³ indicates leukopenia, directly compromising immune function and increasing infection risk. Other lab values (Hb, platelets, glucose) are within normal ranges and not primary indicators of immune dysfunction.

Understanding the Question

This question tests your ability to interpret laboratory values in the context of a clinical presentation. The client’s history of frequent infections over a 6-month period is a classic red flag for an underlying immune deficiency. Your task is to identify which lab value directly reflects the functional capacity of the immune system and, when abnormal, would explain the client’s symptoms.

Analyzing the Laboratory Values

Let’s break down each option to understand its clinical significance and why it does or does not point to compromised immune function.

1. Hemoglobin level of 12.5 g/dL
This value falls within the normal range for an adult female (approximately 12–16 g/dL) and is near the lower end of normal for an adult male (approximately 14–18 g/dL). Hemoglobin is a protein in red blood cells responsible for oxygen transport. A low hemoglobin level indicates anemia, which can cause fatigue and pallor but is not a direct measure of immune competence. The immune system’s primary cellular defense is not reflected in this value.

2. White Blood Cell (WBC) count of 2,800/mm³
This is a critically low value, a condition known as leukopenia. The normal adult WBC count ranges from approximately 4,500 to 11,000/mm³. White blood cells are the cornerstone of the body’s defense against infection. A count this low directly indicates a diminished capacity to fight off pathogens, perfectly aligning with the client’s 6-month history of frequent infections. The foundational research on GATA2 deficiency illustrates this connection clearly, as it is characterized by immunodeficiency and progressive cytopenias, including leukopenia, which directly predispose individuals to recurrent infections and myelodysplastic syndrome ^[2].

3. Platelet count of 250,000/mm³
This value is well within the normal range of 150,000 to 400,000/mm³. Platelets are essential for primary hemostasis and blood clotting. While a low platelet count (thrombocytopenia) would increase the risk for bleeding, a normal count does not explain a susceptibility to infection. Platelets have a secondary, modulatory role in inflammation, but their primary function is not to prevent infection.

4. Blood glucose level of 110 mg/dL
This is a normal, non-fasting or a slightly elevated fasting blood glucose level. While chronic, poorly controlled hyperglycemia (as in diabetes mellitus) can impair immune cell function over time, a single value of 110 mg/dL is not diagnostic of diabetes and would not be the most likely direct cause of frequent infections in this scenario. The question asks for the lab finding that most likely indicates compromised immune function, and a direct measure of immune cells is a more immediate indicator.

The Pathophysiology of Immunodeficiency and Leukopenia

The immune system’s functional integrity is directly dependent on the production and proper function of leukocytes. A state of immunodeficiency, as described in the literature, is a pathological state where this functional integrity is compromised, contributing to disease development . A low WBC count, specifically, can result from decreased production in the bone marrow, increased destruction, or sequestration. The GATA2 gene plays an indispensable role in hematopoiesis and immune regulation, and its deficiency leads to a spectrum of disorders including profound immune dysfunction and cytopenias like monocytopenia and B-cell lymphopenia, which manifest clinically as recurrent infections [1, 2]. In a client presenting with a protracted history of infections, a WBC count of 2,800/mm³ is a direct laboratory correlate of this underlying pathophysiological process, revealing a quantitative defect in the body’s primary defense mechanism.