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Lab Values Indicating Presence of a Diagnosis – Tip Sheet

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HIAcode

Nov 07, 2025

Industry News Medical Coding Tips
Lab Values Indicating Presence of a Diagnosis

Accurate diagnosis coding relies on recognizing the clinical indicators that support or suggest a condition’s presence. This tip sheet highlights key lab values commonly associated with major diagnoses—including heart failure, renal injury, respiratory failure, anemia, liver failure, malnutrition, myocardial infarction, and sepsis. Designed for medical coders and CDI professionals, it serves as a quick reference to help ensure clinical validity, documentation integrity, and coding accuracy. Understanding how abnormal lab results align with diagnoses can strengthen query opportunities and improve compliance across inpatient and outpatient records.

Both coders and CDI specialists must review health record documentation with an eye toward clinical validity. As codes are assigned, the reviewer of the record confirms that the documentation contains enough clinical evidence to support the documented diagnoses being reported. Reviewers must also be able to recognize when clinical indicators of a condition are present in the record but a corresponding diagnosis is not explicitly documented.

Although not definitive on their own, lab values are a significant type of clinical indicator. Standard lab value references provide empirical and widely agreed upon support for the presence or absence of a diagnosis. As such, significant variance in pertinent lab values should be identified and evaluated for consistency with the relevant documentation before code assignments are finalized. Effective evaluation of lab values requires familiarity with what is considered normal or expected results and abnormalities supporting or suggesting the presence of specific diagnoses.

This Coding Tip seeks to highlight indicators of common diagnoses for which lab values are routinely used to support or suggest the diagnosis’ presence. Reference is also made to additional resources that provide an expanded list of standard lab results.

It should be noted that “normal” lab reference ranges often differ based on age, gender or certain physiological states such as pregnancy. The information included here is related to lab values for adults with a resource related to pediatric lab values included in the references. Additionally, reference ranges though generally similar do vary based on source, so a small variation either higher or lower than the reference ranges included here are not likely to be indicative of disease.

Which Lab Values Support/Suggest Certain Diagnoses?

The tables below show the reference range values for lab tests commonly performed to help rule in/out the presence of a specific diagnosis/condition and the values that would indicate the presence of a specific diagnosis/condition. These values should be considered in the context of the complete clinical picture including additional signs/symptoms/reference values for non-lab tests (e.g., blood pressure, pulse oximetry, EKG readings etc.) and treatment.

Acute Heart Failure

 
Lab Test Reference Range Indicators of HF
BNP (B-type Natriuretic Peptide) < 100/125 pg/ml > 500
NT-proBNP (by age)
(N-terminal pro B-type Natriuretic Peptide		 > 125 pg/ml (Under 75)
> 450 pg/ml (Over 75)		 > 450 (Age <50)
> 900 (Age 50-75)
> 1,800 (Age >75)
Notes:
  • Sources vary on reference range values
  • Abnormal values are reflective of patients with no renal impairment

 

Acute Renal Failure/Kidney Injury

 
Lab Test Reference Range Indicators of AKI
Male Female
Creatinine, serum 0.70–1.30 mg/dL 0.50–1.10 mg/dL

  • Increase in creatinine to > 1.5x baseline withing 7 days prior

  • Increase in creatinine > 0.3 mg/dl when comparing two levels, no more than 48 hrs. apart.

  • Urine output < 0.5 mg/kg/hr. for 6 hours
Notes:

  • These are the KDIGO criteria for AKI

  • The criteria are the same for adults and children

  • These criteria apply to patients with/without chronic kidney disease

  • AKI creatinine criteria are applied to patient baseline without regard to reference range

  • If baseline is unavailable, the lowest level obtained during hospitalization is accepted as the baseline

 

Acute Respiratory Failure - Without Chronic Respiratory Failure

 

Lab Test Reference Range Indicators of ARF
ABG -PaO2 > 80 mmHg (room air) PaO2 < 60 mmHg (room air) + normal PaCO2 (Hypoxemic)
ABG – PaCO2 35-45 mmHg (room air) > 50 mmHg (Hypercapnic)
Notes:
  • PaO2 criteria for acute respiratory failure are based on the patient being on room air. If oxygen therapy has been initiated, calculate the P/F ratio

 

Acute Respiratory Failure – With Chronic Respiratory Failure

 

Lab Test Reference Range Indicators of ARF
ABG -PaO2 > 80 mmHg (room air) Hypoxemic < 60 mmHg (on usual home O2) or Decrease in baseline O2 >10
ABG – PaCO2 35-45 mmHg (room air) Hypercapnic PaCO2 > 50 mmHg with pH < 7.35 (ABG) or PCO2 > 55 mmHg with pH < 7.33 (VBG)
pH 7.35 - 7.45  

 

Anemia 

 

Lab Test Reference Range Indicators of Anemia
Male Female Male Female
Hemoglobin 14–18 g/dL 12–16 g/dL < 13.0 < 12.0 < 11.0 (pregnancy)
Hematocrit 42%–50% 37%–47% < 42% < 37%
Note: A smaller decrease in Hgb is more significant with a lower baseline

 

Liver Failure

 

Lab Test Reference Range Indicators of Failure
INR 0.8-1.1 > 1.5
Aminotransferase serum alanine (ALT, SGPT) 10–40 U/L > 3x URL
Aminotransferase, serum aspartate (AST, SGOT) 10–40 U/L > 3x URL
Bilirubin, Serum Total - 0.3–1.0 mg/dL Direct - 0.1–0.3 mg/dL Indirect - 0.2–0.7 mg/dL Elevated above URL
Platelet Count 150,000 – 450,000μL < 150K

Notes:

  • INR values may be affected if patients are taking anticoagulants or vitamin K
  • URL is upper reference limit

 

Malnutrition

 

Lab Test Reference Range Indicators of Inflammation
C-reactive protein (CRP), serum ≤ 0.8 mg/dL 1 to 10 mg/dL (Mild to moderate elevation) 11 to 50 mg/dL (Marked elevation) > 50 mg/dL (Severe elevation)
Albumin, serum 3.5–5.5 g/dL < 3.5 b/dL
Pre-albumin, serum 16–30 mg/dL < 16 mg/dL
Notes:

  • The presence of inflammation is one of the etiologic criteria of the GLIM definition of malnutrition. Elevated CRP and low albumin/prealbumin are indicators of chronic or severe systemic inflammation.

 

Myocardial Infarction

 

Lab Test Reference Range URL/99th Percentile
Male Female Male Female
Troponin I, cardiac, serum ≤ 0.04 ng/mL > 0.04 ng/mL
Troponin T, cardiac, serum ≤ 0.01 ng/mL > 0.01 ng/mL
Troponin I, cardiac, high-sensitivity, plasma ≤ 20 ng/L ≤ 14 ng/L ≤ 21 ng/L ≤ 15 ng/L
Troponin T, cardiac, high-sensitivity, plasma ≤ 15 ng/L ≤ 10 ng/L ≤ 16 ng/L ≤ 11 ng/L
Notes:
  • Sources vary slightly on reference range values
  • URL is upper reference limit
  • Elevated troponin is suggestive of myocardial injury only. Other clinical factors must be considered to make a diagnosis of myocardial infarction.
  • For high sensitivity troponins, elevations >5x the URL have a higher predictive value for MI

 

Sepsis 2

 

Lab Test Reference Range Indicators of Sepsis
Glucose, plasma (fasting) 70–99 mg/dL > 140 mg/dL
Leukocytes WBC - 4000–11,000/μL Bands – 0% - 5% WBC - > 12,000 - <4,000 Bands - >10%
C-reactive protein, serum ≤0.8 mg/dL Elevated (> reference range)
C-reactive protein, serum high sensitivity Low cardiovascular risk: ˂ 1.0 mg/L Average cardiovascular risk: 1.0–3.0 mg/L High cardiovascular risk: > 3.0 mg/L Elevated (> reference range)
Procalcitonin, serum ≤ 0.10 ng/mL Elevated (> reference range)
Lactate, serum/plasma 0.7–2.1 mmol/L > 2.0 (Sepsis) > 4.0 (Septic Shock)
Organ Dysfunction Values
Creatinine, serum Male Female Increase > 0.5
0.70–1.30 mg/dL 0.50–1.10 mg/dL
INR or PTT or Thrombocytopenia 0.8-1.1 11–13 seconds 150,000 to 450,000/mcL > 1.5 > 60 seconds <100,000/mcL
Notes:
  • Sepsis is a complicated condition with many interrelated clinical indicators. This table only presents lab values indicative of sepsis. Evaluate this information within the full context of the patient’s clinical presentation. Patients may or may not have any of these diagnostic criteria and their presence or absence alone is not a definitive indication of sepsis or lack of sepsis.

 

Sepsis 3

 

Lab Test SOFA Scale Points
0 1 2 3 4
Respiratory PaO2/FIO2 > 400 < 400 < 300 < 200 with resp support < 100 with resp support
Coagulation Platelet Count > 150,000 < 150,000 < 100,000 < 50,000 < 20,000
Hepatic Bilirubin (mg/dL) < 1.2 1.2-1.9 2.0-5.9 6.0-11.9 > 12
Renal Creatinine (mg/dL) < 1.2 1.2-1.9 2.0-3.4 3.5-4.9 > 5.0
Notes:
  • Sepsis 3 defines sepsis as an infection with acute organ dysfunction
  • Organ dysfunction is a 2 point increase, from the patient’s baseline, of the SOFA score using 6 organ systems
  • The baseline SOFA score for an organ system is assumed to be “0” if the baseline is unknown and the patient has no known preexisting dysfunction
  • This table only addresses the organ systems whose function is measured with lab tests (e.g., Renal organ system function is evaluated by creatinine levels which are measured with a lab test)
  • Sepsis 3 criteria applies only to adults

 

Helpful Resources

Much of the information presented above is a summary of the information included in the resources listed below. It’s recommended that you also visit these resources and give them an in-depth review to make yourself well acquainted with the lab values that support diagnosis code assignment or suggest a query for clinical validity.

Title Publisher URL Paid/Free
CDI Pocket Guide Pinson and Tang 2024 CDI Pocket Guide® - The Original By Pinson & Tang Paid
Laboratory Test Reference Ranges American Board of Internal Medicine laboratory-reference-ranges.pdf Free
Laboratory Reference Ranges in Healthy Adults Medscape Lab Values, Normal Adult: Laboratory Reference Ranges in Healthy Adults Free
Reference Ranges Document (Pediatric) Children’s Hospital of Philadelphia chop-labs-reference-ranges.pdf Free

 

References

Frequently Asked Questions

Why are lab values important for clinical validation in coding?

Lab values provide objective evidence to support or question a documented diagnosis. When coders and CDI professionals compare test results against reference ranges, they can determine whether the documentation accurately reflects the patient’s condition and identify when a clinical query may be needed to clarify inconsistencies.

How should coders use abnormal lab values when assigning diagnosis codes?

Abnormal lab results should never be coded as standalone diagnoses. Instead, they should be used to support or prompt further provider documentation. Coders should reference the entire clinical picture—including signs, symptoms, treatment, and provider notes—before finalizing code assignments.

Do reference ranges for lab values vary between sources?

Yes. Normal lab reference ranges can differ slightly by facility, testing method, age, gender, and physiological state (such as pregnancy). Coders should always refer to the reference values provided in the facility’s laboratory system or clinical documentation to ensure the most accurate interpretation.

For more than 30 years, HIA has been the leading provider of compliance audits, coding support services and clinical documentation audit services for hospitals, ambulatory surgery centers, physician groups and other healthcare entities. HIA offers PRN support as well as total outsource support.

The information contained in this coding advice is valid at the time of posting. Viewers are encouraged to research subsequent official guidance in the areas associated with the topic as they can change rapidly.

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