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.

Core Nursing Explanation Key Concept Analysis: This question assesses your ability to link a clinical symptom—frequent infections—to the most relevant laboratory indicator of immune system compromise. The immune system's primary cellular defenders are white blood cells (WBCs), also known as leukocytes. A low WBC count, or leukopenia, directly impairs the body's ability to fight off pathogens, leading to increased susceptibility to infections.

Answer Rationale: Key Point! A White blood cell count of 2,800/mm³ is the correct answer because it represents leukopenia. The normal adult WBC range is typically 5,000–10,000/mm³. A value of 2,800/mm³ is significantly below this range, indicating a deficient number of infection-fighting cells. This is the most direct laboratory evidence explaining the client's history of frequent infections.

Distractor Analysis:
Watch out for confusion! Option ①: A Hemoglobin level of 12.5 g/dL is within the normal range for an adult female (typically 12-16 g/dL) and for an adult male (typically 13.5-17.5 g/dL). While severe anemia can cause general weakness, it is not the primary lab marker for immune dysfunction.
Option ③: A Platelet count of 250,000/mm³ is well within the normal range (150,000–400,000/mm³). Platelets are crucial for clotting, not for fighting infections.
Option ④: A Blood glucose level of 110 mg/dL is at the high end of normal fasting glucose (70–110 mg/dL) or could be considered impaired fasting glucose. While chronic hyperglycemia (as seen in uncontrolled diabetes) can impair immune function and increase infection risk, a single value of 110 mg/dL is not diagnostic of that condition and is not the most direct indicator of immune compromise in this scenario.

Related Concepts: It's important to understand the components of a Complete Blood Count (CBC) and their functions. While a low total WBC count indicates leukopenia, a differential count (breaking down the types of WBCs like neutrophils, lymphocytes) provides more specific information. For example, neutropenia (low neutrophil count) is a particularly critical form of leukopenia that poses a high risk for bacterial infections. Concept Summary

Concept	Description	Clinical Implication
Leukopenia	Abnormally low white blood cell (WBC) count (< 4,000/mm³).	Primary lab indicator of compromised immune function; increased risk of infection.
Complete Blood Count (CBC)	A common blood test that measures the cellular components of blood.	Key diagnostic tool; includes WBCs, RBCs, hemoglobin, hematocrit, and platelets.
Neutropenia	A severe subtype of leukopenia involving low neutrophil count.	Extremely high risk for bacterial infections; requires protective isolation (neutropenic precautions).
Anemia	Low red blood cell count or hemoglobin.	Causes fatigue and decreased oxygen delivery; not a direct cause of frequent infections.

Side-by-Side Comparison!

Lab Value	Normal Range (Adult)	Condition if Low	Primary Clinical Concern
White Blood Cell (WBC)	5,000–10,000/mm³	Leukopenia	Infection risk (Immune compromise)
Hemoglobin (Hgb)	F: 12–16 g/dL M: 13.5–17.5 g/dL	Anemia	Fatigue, hypoxia (Oxygen transport issue)
Platelet (Plt)	150,000–400,000/mm³	Thrombocytopenia	Bleeding risk (Clotting issue)

Anatomy, Physiology & Pharmacology Points The bone marrow is the primary site for the production of all blood cells (hematopoiesis). Conditions like bone marrow suppression (from chemotherapy, radiation, certain medications, or diseases) can lead to pancytopenia (low counts of all cell lines), including leukopenia. Drugs such as chemotherapeutic agents and some antibiotics (e.g., trimethoprim-sulfamethoxazole) are common causes of drug-induced leukopenia/neutropenia. Memory Tips Think "LOW WBC = LOW Defense": Leukopenia means your body's army (WBCs) is understaffed, leaving you vulnerable to invaders (infections).
Normal Range Mnemonic for WBCs: "5 to 10 is the typical scene" (5,000–10,000/mm³). High-Frequency NCLEX Topics Interpreting CBC results, especially identifying values indicative of infection, bleeding risk, or anemia, is a Core NCLEX skill. You will often be asked to prioritize care based on abnormal lab values (e.g., neutropenic precautions for a low WBC, bleeding precautions for low platelets). Recognizing leukopenia as a cause for frequent infections is a classic application question. Watch Out for Question Variations! * Shift from Assessment to Intervention: "The nurse notes a client's WBC is 2,500/mm³. Which action should the nurse take first?" (Answer: Initiate neutropenic/precautions to prevent infection). * Shift to Medication Side Effect: "A client on chemotherapy has a WBC of 1,800/mm³. The nurse identifies this as a potential side effect of which medication?" (Linking the lab value to the drug's myelosuppressive effect). * Prioritization with Multiple Abnormal Labs: A client has a WBC of 2,000/mm³, Hgb of 7.8 g/dL, and platelets of 20,000/mm³. Which finding requires the most immediate intervention? (Often, the lowest platelet count indicating imminent bleeding risk may be prioritized over infection risk, depending on the exact values and clinical context).

Nursing Clinical Practice Guide Clinical Scenario: You are caring for Mr. Johnson, a 58-year-old receiving chemotherapy for lymphoma. During your morning assessment, he mentions feeling more tired than usual and has a slight cough. You review his morning labs.

Nursing Intervention Strategy: 1. Assessment: Check the CBC results immediately. Note the total WBC and, crucially, the absolute neutrophil count (ANC). An ANC < 1,000/mm³ indicates neutropenia, and < 500/mm³ indicates severe neutropenia, requiring strict precautions. Assess vital signs, especially temperature (fever may be the only sign of infection in neutropenic patients). Perform a focused respiratory assessment for the cough. 2. Planning & Implementation: If neutropenic, implement neutropenic precautions (also called protective isolation): private room if possible, strict hand hygiene for everyone, no fresh flowers or standing water, no raw fruits/vegetables, avoiding crowds and sick visitors. Administer prescribed colony-stimulating factors (e.g., filgrastim) to stimulate WBC production. Educate the patient and family on infection prevention at home. 3. Evaluation: Monitor for signs of infection (fever, chills, new cough, dysuria, skin changes). Track serial CBCs to see if the WBC count is recovering.

Patient Safety and Precautions: In a neutropenic patient, a fever is a medical emergency. Do not delay reporting a temperature of 100.4°F (38°C) or higher on a single reading, or 100°F (37.8°C) sustained over an hour. Anticipate orders for STAT blood cultures and broad-spectrum antibiotics. Nursing Procedure & Medication Flow Key Procedure: Implementing Neutropenic Precautions * Hand Hygiene: Meticulous handwashing with soap and water or alcohol-based gel by staff and visitors BEFORE and AFTER contact. * Environment: Private room is ideal. Daily cleaning. No plants or vases with standing water. * Diet: Provide a low-bacterial diet (no uncooked fruits/vegetables, well-cooked meats, only pasteurized dairy). * Personal Hygiene: Encourage daily bathing. Use electric razors instead of blades to avoid nicks. Perform meticulous oral care to prevent mucositis.
Medication: Colony-Stimulating Factors (e.g., Filgrastim) * Action: Stimulates the bone marrow to produce neutrophils. * Administration: Usually given as a subcutaneous injection. * Nursing Considerations: Monitor for bone pain (a common side effect). Teach self-injection techniques for outpatient therapy. A Word from Your Senior Nurse "Remember, lab values are not just numbers on a page—they are vital signs of your patient's internal state. A dropping WBC count is a silent alarm bell for infection risk. In clinical practice, you are the one who connects the dots between the patient saying 'I don't feel right' and that critical lab value. When you see leukopenia, your nursing brain should immediately switch to 'infection prevention mode.' This proactive, assessment-driven mindset is what makes a great nurse and is exactly what the NCLEX is testing. Always ask yourself: 'What is this lab value telling me about my patient's safety, and what should I do about it?'"