Unexpectedly low pulse oximetry measurements associated with variant hemoglobins: A systematic review Journal Articles uri icon

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abstract

  • AbstractPulse oximetry estimates arterial blood oxygen saturation based on light absorbance of oxy‐ and deoxy‐hemoglobin at 660 and 940 nm wavelengths. Patients with unexpectedly low SpO2 often undergo cardio‐pulmonary testing to ascertain the cause of their hypoxemia. However, in a subset of patients, a variant hemoglobin is responsible for low SpO2 measurements. The extent of this problem is unclear. We performed a systematic literature review for reports of low SpO2 associated with variant hemoglobins. We also reviewed unpublished cases from an academic hemoglobin diagnostic reference laboratory. Twenty‐five publications and four unpublished cases were identified, representing 45 patients with low SpO2 and confirmed variant hemoglobin. Fifty‐seven family members of patients had confirmed or suspected variant hemoglobin. Three low oxygen affinity variant hemoglobins had concordantly low SpO2 and SaO2. Eleven variant hemoglobins were associated with unexpectedly low SpO2 measurements but normal SaO2. Hemoglobin light absorbance testing was reported in three cases, all of which showed abnormal absorption spectra between 600 and 900 nm. Seven other variant hemoglobins had decreased SpO2, with unreported or uncertain SaO2. Twenty‐one variant hemoglobins were found to be associated with low SpO2. Most variant hemoglobins were associated with spuriously low SpO2. Abnormal absorption spectra explain the discrepancy between SpO2 and SaO2 for some variants. The differential diagnosis of possible variant hemoglobin ought to be considered in asymptomatic patients found to have unexpectedly low SpO2. The correct diagnosis will help to spare patients from unnecessary investigations and anxiety. Am. J. Hematol., 2010. © 2010 Wiley‐Liss, Inc.

publication date

  • November 2010