Erratum to: Unexpectedly low pulse oximetry measurements associated with variant hemoglobins: A systematic review

Abstract

Pulse 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 We also reviewed unpublished cases from an academic hemoglobin diagnostic reference laboratory. Twenty‐five publications and four unpublished cases were identified, representing 45 patients with low SpO2 and confirmed variant hemoglobin.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. 86:722–725, 2011. © 2011 Wiley‐Liss, Inc.

How we diagnose and manage altered oxygen affinity hemoglobin variants

“…With this understanding, in a case of a suspected altered oxygen affinity variant, the clinician is empowered to conduct the appropriate diagnostic investigations, specifically Hb separation studies (with or without globin gene DNA testing to identify a variant Hb) and blood p50 testing. Patients with low affinity variants should also have ABG studies and pulse oximetry in order to identify if there is true hypoxemia (low SaO 2 and low SpO 2 ) or a saturation gap (low SpO 2 with normal SaO 2 ) suggesting artifactually low SpO 2 due to altered light absorbance pattern of the variant Hb . Our patient with Hb Kirksey received a final diagnosis of a low oxygen affinity Hb variant more than 8 years after the first low SpO 2 was recorded, after extensive cardiorespiratory evaluation.…”

“…Asymptomatic anemia is a common physiologic consequence of decreased oxygen affinity, with increased oxygen delivery to the tissues leading to compensatory decrease in erythropoiesis. Chronically low SpO 2 has been documented in patients with a number of low oxygen affinity variants, including Hb Rothschild, Bassett and Chico . Incongruence between the patient's clinically stable physical evaluation and low SpO 2 is explained by increased tissue oxygen delivery by the low affinity variant .…”

“…Arterial blood gas is a crucial ancillary test that must be interpreted in conjunction with pulse oximetry readings in patients with low SpO 2 who are suspected or known to have an altered oxygen affinity Hb variant. Low oxygen affinity Hb variants will typically have low SpO 2 readings accompanied by low SaO 2 , with no evidence of cardiac or respiratory disease . Examples of such Hbs include Hb Bassett, Hb Rothschild and Hb Canebiere .…”

“…Low oxygen affinity Hb variants will typically have low SpO 2 readings accompanied by low SaO 2 , with no evidence of cardiac or respiratory disease . Examples of such Hbs include Hb Bassett, Hb Rothschild and Hb Canebiere . There are also a subset of low affinity variants with low SpO 2 and normal SaO 2 (eg, Hb Titusville and Hb Bonn) .…”

“…Examples of such Hbs include Hb Bassett, Hb Rothschild and Hb Canebiere . There are also a subset of low affinity variants with low SpO 2 and normal SaO 2 (eg, Hb Titusville and Hb Bonn) . Variants with this unusual pattern have falsely low SpO 2 measurements due to abnormal absorption spectra of the variant Hb at wavelengths emitted by the pulse oximeter.…”