Checklist: Interpreting CKD Lab Results

Chronic kidney disease (CKD) progresses slowly, making it crucial to interpret lab results correctly for better care. Here’s a quick guide to help you evaluate CKD lab tests:

• GFR (Glomerular Filtration Rate): The key marker for kidney function. A GFR below 60 mL/min signals CKD.
• BUN (Blood Urea Nitrogen): High levels (above 20 mg/dL) can indicate kidney issues.
• Creatinine: Elevated levels often reflect reduced kidney function. Normal ranges:
  • Males: 0.7–1.3 mg/dL
  • Females: 0.6–1.1 mg/dL
• Urine ACR (Albumin-to-Creatinine Ratio): Measures protein leakage, a sign of kidney damage.
  • Normal: <30 mg/g
  • Moderate: 30–300 mg/g
  • Severe: >300 mg/g

5 Steps to Review CKD Lab Results:

1. Verify test accuracy (repeat tests if needed).
2. Identify the CKD stage using GFR and ACR.
3. Monitor trends over time (e.g., GFR decline).
4. Consider patient history (medications, illnesses, etc.).
5. Assess risk factors (blood pressure, diabetes, BMI, etc.).

Understanding Your Kidney Labs: eGFR, Creatinine, BUN …

Main Lab Tests for CKD

Understanding key lab tests is essential for evaluating kidney function in CKD. Below are the primary tests used and what they measure.

GFR Measurement

GFR (glomerular filtration rate) is a crucial indicator of kidney function. A GFR above 90 mL/min/1.73 m² is considered normal. Lower values may suggest CKD and are classified as follows:

GFR Range (mL/min/1.73 m²)	CKD Stage	Kidney Function
≥90	Stage 1	Normal to High
60–89	Stage 2	Mildly Decreased
30–59	Stage 3	Moderately Decreased
15–29	Stage 4	Severely Decreased
<15	Stage 5	Kidney Failure

BUN Levels

BUN (blood urea nitrogen) measures the amount of urea in the blood, which can indicate kidney function. Normal levels range from 7–20 mg/dL. Levels exceeding 50 mg/dL may point to severe kidney issues.

Creatinine Testing

Serum creatinine offers another measure of kidney filtration. Normal levels depend on age and gender:

• Adult males: 0.7–1.3 mg/dL
• Adult females: 0.6–1.1 mg/dL

A significant rise in creatinine, such as a doubling, often reflects a 50% drop in GFR.

Urine ACR Testing

The Albumin-to-Creatinine Ratio (ACR) measures protein leakage in urine, a sign of kidney damage. Results are categorized as follows:

ACR Level (mg/g)	Classification	Meaning
<30	Normal	No albuminuria
30–300	Moderate	Early signs of damage
>300	Severe	Significant kidney damage

Higher ACR levels indicate ongoing kidney damage and a greater risk of disease progression. Regular ACR checks are essential for monitoring treatment and managing CKD effectively.

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5-Step CKD Lab Result Review

1. Verify Test Accuracy

Make sure tests are spaced at least three months apart. Confirm that samples were collected and processed correctly, results align with the lab’s reference ranges, and pre-test instructions (like fasting or medication adjustments) were followed.

If there’s a sudden drop in GFR, repeat the tests right away to rule out acute kidney injury.

2. Identify CKD Stage

Use GFR and uACR values to evaluate the condition’s severity:

GFR Category	uACR Category	Risk & Action
≥90 mL/min	30–300 mg/g	Stage 1 – moderate risk
60–89 mL/min	>300 mg/g	Stage 2 – high risk
30–59 mL/min	Any level	Stage 3 – consider specialist referral
<30 mL/min	Any level	Stage 4/5 – urgent specialist care

3. Monitor Trends

Compare the current GFR to the baseline. Calculate GFR decline (a normal rate is about 0.7–1 mL/min per year), watch for sudden changes in creatinine or BUN, and keep an eye on increasing uACR levels.

Also, factor in the patient’s medical history to better understand lab trends.

4. Evaluate Patient History

Take into account factors that could influence results, such as:

• Medications affecting kidney function
• Diabetes or high blood pressure
• Recent illnesses or dehydration
• Changes in diet or exercise
• Past kidney injuries or procedures

5. Assess Risk Factors

Regularly monitor and address these issues:

• Blood pressure above 130/80 mm Hg
• HbA1c levels over 7% in diabetic patients
• uACR higher than 30 mg/g
• BMI over 30
• Smoking habits
• Medication adherence

Evaluate these factors every 3–6 months and adjust treatment plans as needed.

Common Lab Reading Mistakes

Confusing Acute and Chronic Changes

To distinguish between AKI (Acute Kidney Injury) and CKD (Chronic Kidney Disease), focus on sequential lab trends along with historical data. AKI is marked by sudden changes, while CKD shows a slow, progressive decline. Reviewing lab results over time can clarify whether the changes are acute or chronic. Understanding this difference is key to avoiding errors in interpretation.

Summary and Action Steps

To improve your approach to reviewing CKD lab results, follow this practical action plan:

• Systematically interpret CKD lab results to ensure accuracy and consistency.
  • Double-check test accuracy and monitor trends in GFR, BUN, creatinine, and urine ACR.
  • Record any changes to track disease progression.
  • Factor in the patient’s history alongside current lab values.
  • Evaluate risk factors that could influence the results.

When applying these steps, keep these key points in mind:

• Pay close attention to how lab values change over time.
• Look at the full clinical picture, including medications and other health conditions.
• Use the correct reference ranges, tailored to the patient’s demographic details.

These guidelines reinforce the clinical decision-making skills required for safe patient care and exam preparation. For more resources, including study materials and practice scenarios, check out the Nurse Cram NCLEX Exam Review website.

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