**Core Concept:** Polymorphonuclear neutrophils (PMNs) are a type of white blood cell (WBC) that play a crucial role in the immune system's response to infection and inflammation. In a healthy child, their absolute count (number of cells per microliter) should be within a normal range (4,000-11,000 cells/μL).

**Why the Correct Answer is Right:**

In this scenario, we are dealing with a child with an abnormal polymorphonuclear neutrophil count on a routine complete blood count (CBC). The correct answer is to perform a complete blood count (CBC) with differential count, which is essential for assessing the distribution and maturation stages of all WBCs, including neutrophils. The differential count provides the percentage of each type of WBC in the blood sample.

**Why Each Wrong Option is Incorrect:**

A. Performing a routine CBC alone is not sufficient to diagnose the cause of elevated PMNs. A complete blood count without differential count is inadequate.
B. The decision to treat the elevated PMNs depends on the increased count's cause, which is not addressed by this option.
C. Although referral to a pediatrician is important for overall child health, it does not directly address the issue of the abnormal PMNs.
D. The statement about the PMNs being elevated due to sepsis is incorrect; sepsis is a clinical syndrome, not a cause for elevated PMNs. The cause should be determined first.

**Clinical Pearl:**

To effectively manage a child with an elevated PMN count, we need a complete blood count (CBC) with differential count to determine the specific cause of the elevated PMNs. This will guide further diagnostic and therapeutic decisions.

**Correct Answer:**

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