A Family of Three with Haemoglobin Cheverly: Low Oxygen Saturation in Stable Patients

Abstract

Haemoglobin (Hb) Cheverly is a rare, low oxygen affinity haemoglobinopathy. It is a result of point mutation at the 45 codon of the beta globin genes that leads to substitution of phenylalanine by serine. It is characterised by spuriously low peripheral oxygen saturation with normal arterial oxygen saturation. We describe a family of three with Hb Cheverly in Sarawak General Hospital, Malaysia. It was discovered through incidental finding during hospital admission for unrelated complaints. Laboratory testing revealed abnormal haemoglobin detected at the C window of the high performance liquid chromatography. Subsequent DNA analysis detected replacement of thymidine by cytosine at the beta globin genes. Hb Cheverly may or may not have clinical significance as most of the patients live a normal life; however, it is crucial for us to make early diagnosis to prevent unnecessary extensive investigations for hypoxaemia detected via pulse oximetry, especially in the midst of COVID-19 pandemic.

Understanding pulse oximetry in hematology patients: Hemoglobinopathies, racial differences, and beyond

“…1,22,29 Hemoglobin Cheverly is another unstable hemoglobin with increased absorption in the red region resulting in underestimation of SpO 2 . 1,22,27 Hemoglobin Lancing is a normal oxygen affinity hemoglobin that has an abnormal pattern of light absorption, resulting in underestimation of SpO 2 . 1 Methemoglobins also have an abnormal absorption spectrum, and have increased absorption in both the red and the near infrared regions, resulting in a SpO 2 which is difficult to interpret.…”

“…Hemoglobin variants resulting in reduced oxygenation (SpO 2 and/or SaO 2 ) through low oxygen affinity, unstable hemoglobins or methemoglobin are rare and often only published in case reports or small case series 25,26 . Although rare, unexpectedly abnormal SpO2 in these patients can lead to confusion and unnecessary series of cardiorespiratory investigations 24,27 …”

“…Several hemoglobin variants are associated with a low SpO 2 but a normal SaO 2 level 22 . Several of these hemoglobinopathies result in this pattern due to a difference in absorbance profile as compared to hemoglobin A 22,27 . When there is an increase in absorption in the red spectrum, it increases the numerator of the ratio of ratios and therefore results in a reduction in the SpO 2 that is not reflective of oxygenation.…”

“…Hemoglobin Bonn has a peak of absorption in the red region similar to methylene blue, which results in a discordant SpO 2 which is underestimated 1,22,29 . Hemoglobin Cheverly is another unstable hemoglobin with increased absorption in the red region resulting in underestimation of SpO 2 1,22,27 . Hemoglobin Lancing is a normal oxygen affinity hemoglobin that has an abnormal pattern of light absorption, resulting in underestimation of SpO 2 1 …”

“…25,26 Although rare, unexpectedly abnormal SpO2 in these patients can lead to confusion and unnecessary series of cardiorespiratory investigations. 24,27 Several hemoglobinopathies have a low affinity for oxygen and result in a rightward shift of the oxygen dissociation curve, resulting in low SpO 2 and SaO 2 and facilitated oxygen delivery to the tissue.…”