Abstract Introduction Pulse oximetry (SpO2) is ubiquitous in screening for hypoxemia but can be misleading in the presence of hemoglobin variants. We report a young adult with years of low SpO2 readings, ultimately attributed to delta-beta thalassemia, recognized during preconception evaluation. Case Report A 30-year-old woman with no significant medical history was referred to the pulmonology clinic for chronically low SpO2 (83-88%), first noted in medical school and reproduced on multiple devices and sites. She denied dyspnea, chest pain, cough, wheeze, or exercise intolerance; she tolerated commercial flights without symptoms. Family is of Caribbean ancestry; no known hemoglobinopathy. When seen in our clinic, vital signs in clinic again showed SpO2 84% on room air. Arterial blood gas from 2024 on room air: pH 7.44, PaCO2 36 mm Hg, PaO2 162 mm Hg. Complete blood count showed microcytosis with hemoglobin of 11.8-12.5 g/dL and low mean corpuscular hemoglobin. Chest radiograph, pulmonary function tests, and transthoracic echocardiogram were normal. Hemoglobin electrophoresis performed during preconception work-up was consistent with delta-beta thalassemia; fetal hemoglobin (HbF) was elevated. Iron studies showed iron deficiency (ferritin 29.5 ng/mL). Hematology recommended folic acid and oral iron; genetic counseling and partner testing were arranged. Obstetric care proceeded without cardiopulmonary limitations. Discussion This case illustrates spurious hypoxemia due to pulse oximetry artifact in a hemoglobinopathy. Hemoglobin variants and elevated HbF can alter light absorption at 660/940 nm, producing falsely low SpO2 despite normal PaO2 and oxygen content.i, ii, iii The patient’s normal ABG, normal cardiopulmonary testing, microcytosis, and electrophoresis pointed away from pulmonary shunt/ventilation-perfusion mismatch and toward a hematologic etiology.iv Recognizing this pitfall prevents unnecessary imaging, admissions, or oxygen therapy - particularly crucial in pregnancy, when inaccurate saturation readings can trigger avoidable interventions and anxiety. Awareness of delta-beta thalassemia as a cause of low pulse oximetry readings can refine diagnostic reasoning and optimize maternal-fetal care. References: i Madeleine Verhovsek et al., “Unexpectedly Low Pulse Oximetry Measurements Associated with Variant Hemoglobins: A Systematic Review,” American Journal of Hematology 85, no. 11 (2010): 882-85, https://doi.org/10.1002/ajh.21810. ii Alistair Robertson and Amin Rahemtulla, “Pulse Oximetry Error in a Patient with a Santa Ana Haemoglobinopathy,” BMJ Case Reports 2016 (September 2016): bcr2016216787, https://doi.org/10.1136/bcr-2016-216787. iii Amal Jubran, “Pulse Oximetry,” Critical Care (London, England) 19, no. 1 (2015): 272, https://doi.org/10.1186/s13054-015-0984-8. iv Madeleine Verhovsek et al., “Unexpectedly Low Pulse Oximetry Measurements Associated with Variant Hemoglobins: A Systematic Review,” American Journal of Hematology 85, no. 11 (2010): 882-85, https://doi.org/10.1002/ajh.21810. This abstract is funded by: None
Gul et al. (Fri,) studied this question.