Section 7.1 Laboratory

Laboratory Report #26

Date

Collection Date: July 26, 2022
Report Date: August 5, 2022

Laboratory

Quest Diagnostics

Performing Laboratory:
Mayo Clinic Laboratories
Rochester, Minnesota

Ordering Physician

Dr. Maryam Saifi

Report Type

Specialized Allergy / Mast Cell Evaluation

Laboratory testing included:

24-Hour Urine Leukotriene E4 (LTE4)
24-Hour Urine Creatinine
Urine Volume
Collection Duration

Original Report

PDF: Quest Diagnostics – July 26, 2022 (24-Hour Urine Leukotriene E4)

One-Page Summary

Purpose of Testing

This specialized laboratory evaluation was performed as part of the investigation for mast cell activation disorders. Leukotriene E4 (LTE4) is a urinary marker of leukotriene production, a pathway involved in mast cell activation and allergic inflammatory responses.

This test was the fourth component of the July 2022 mast cell evaluation series and was performed alongside:

Serum Tryptase
24-Hour Urine N-Methylhistamine
24-Hour Urine 2,3-Dinor-11β-Prostaglandin F2α

Major Findings

24-Hour Urine Leukotriene E4 (LTE4)

Result

139 pg/mg Creatinine

Reference Range:

≤104 pg/mg Creatinine

Flag: High

Interpretation

The urinary LTE4 level was mildly elevated above the laboratory reference range.

This finding indicates:

Increased leukotriene activity was detected at the time of testing.
The result may be consistent with increased mast cell mediator activity.
However, this test alone is not diagnostic of mast cell activation syndrome or systemic mastocytosis.

The laboratory specifically notes that:

LTE4 greater than 104 pg/mg creatinine may be consistent with systemic mast cell disease.
Clinical sensitivity of LTE4 alone is limited.
Interpretation should occur in combination with other mast cell markers and the patient’s clinical condition.

Collection Quality

Twenty-Four-Hour Urine Collection

Collection Duration

24 hours

Urine Volume

2,200 mL

24-Hour Creatinine

1,342 mg/24 hr

Reference Range:

930–2,955 mg/24 hr

Creatinine Concentration

61 mg/dL

Interpretation

The urine collection was adequate and complete. The normal creatinine excretion supports the reliability of the LTE4 result.

Clinical Significance

This report is important because it is the only abnormal result among the four July 2022 mast cell-related studies.

The complete mast cell evaluation shows:

Test	Result
Serum Tryptase	Normal
Urine N-Methylhistamine	Normal
Urine 2,3-Dinor-11β-Prostaglandin F2α	Normal
Urine Leukotriene E4	Mildly Elevated

The isolated LTE4 elevation suggests that one pathway of mast cell mediator activity may have been increased, but the absence of elevation in the other markers makes a systemic mast cell disorder less certain.

Medication Consideration

The laboratory included an important caution:

Aspirin use within two weeks before testing may decrease LTE4 levels.
NSAID use within 72 hours may affect results.

This information should be considered when interpreting the result in relation to medication history.

Overall Interpretation

This laboratory evaluation demonstrated a mild elevation of urinary Leukotriene E4 during a comprehensive mast cell evaluation. While this result suggests increased leukotriene pathway activity, it must be interpreted with the other mast cell markers. Because serum tryptase, urinary N-methylhistamine, and urinary prostaglandin testing were normal, the overall laboratory pattern does not clearly establish systemic mast cell disease.

Instead, this result represents a possible isolated abnormality requiring correlation with symptoms, clinical history, and physician assessment.

Longitudinal Significance

This report contributes to:

Allergy / Immunology Evaluation
Mast Cell Disorder Evaluation
Differential Diagnosis Archive
Rheumatology Consultation Summary
Systemic Inflammatory Illness Timeline
Medical History Timeline

Clinical Importance

⭐⭐⭐⭐ Important Diagnostic Finding

Unlike the previous mast cell studies, this report contains an abnormal result. It is therefore particularly valuable in the Health Inventory because it documents the one area where mast cell-related testing showed a possible signal.

However, the significance is limited by the fact that:

The elevation was modest.
Other mast cell markers were normal.
No single laboratory test confirms or excludes mast cell activation syndrome.

Key Findings

Urine Leukotriene E4: 139 pg/mg Creatinine
Reference Range: ≤104 pg/mg Creatinine
Interpretation: Mildly elevated
24-Hour Creatinine: 1,342 mg/24 hr (Normal)
Urine Volume: 2,200 mL
Collection Duration: 24 hours

Related Reports

July 26, 2022 – Serum Tryptase Evaluation
July 26, 2022 – 24-Hour Urine N-Methylhistamine Evaluation
July 26, 2022 – 24-Hour Urine 2,3-Dinor-11β-Prostaglandin F2α Evaluation
Autoimmune Evaluation
Allergy / Immunology Evaluation
Rheumatology Consultation Summary
Systemic Inflammatory Illness Timeline

Navigation

Previous Report: July 26, 2022 – 24-Hour Urine 2,3-Dinor-11β-Prostaglandin F2α Evaluation
Next Report: Subsequent Laboratory Evaluation
Return to Laboratory Library
Return to Health Inventory

Observation

This report adds an important nuance to the mast cell evaluation. The earlier three studies were completely normal, but this fourth marker showed a mild elevation.

The most accurate summary of the July 2022 mast cell workup is:

Three normal mast cell markers with one mildly elevated leukotriene marker.

This pattern does not provide a clear diagnosis of mast cell disease, but it does document a possible area for physician review. In the final Health Inventory, this report should be included under Section 3.7 – History of Systemic Inflammatory Illness and Section 7 – Laboratory Archive because it represents part of the extensive effort to understand the cause of the 2021 inflammatory episode.