Hb Grifton [α87(F8)His→Pro; HBA1: C.263A > C (or HBA2)] Causes Abnormal Pulse Oximetry Measurements

Area of Science:

• Hematology
• Clinical Diagnostics

Background:

• Asymptomatic individuals presenting with low transcutaneous pulse oximetry (SpO2) readings can be challenging to diagnose.
• Normal arterial blood gas analyses may conflict with SpO2 readings, suggesting an artifact rather than true hypoxia.

Purpose of the Study:

• To identify the etiology of discordant SpO2 and arterial blood gas results in an asymptomatic toddler and his mother.
• To investigate the impact of a specific hemoglobin variant on pulse oximetry measurements.

Main Methods:

• Newborn screening identified an abnormal hemoglobin variant (Hb Grifton).
• Clinical observation of shared SpO2 and blood gas discordance between mother and child.
• Spectrophotometric analysis to compare light absorption properties of Hb Grifton and Hb A.

Main Results:

• The Hb Grifton variant demonstrated different light absorption characteristics compared to normal adult hemoglobin (Hb A).
• This difference in light absorption led to inaccurate, falsely low SpO2 readings.
• The mother and child consistently showed these abnormal SpO2 readings without clinical signs of hypoxia.

Conclusions:

• Variant hemoglobins can cause erroneous pulse oximetry readings, mimicking true hypoxia.
• Clinical suspicion and appropriate laboratory testing are crucial for diagnosing variant hemoglobinopathies.
• Correct diagnosis prevents unnecessary medical interventions for patients with artifactually low SpO2.