Diagnostic Strategies in Hemoglobinopathy Testing, the Role of a Reference Laboratory in the USA

Abstract

Although commonly assessed in the context of microcytosis or sickling syndrome screening, hemoglobin mutations may not be as readily considered as a cause of other symptoms. These include macrocytosis with or without anemia, chronic or episodic hemolysis, neonatal anemia, erythrocytosis, cyanosis/hypoxia and methemoglobinemia/ sulfhemoglobinemia. Hemoglobin disorders commonly interfere with the reliability of Hb A1c measurement. Because the clinical presentation can be varied and the differential diagnosis broad, a systematic evaluation guided by signs and symptoms can be effective. A tertiary care reference laboratory is particularly challenged by the absence of pertinent clinical history and relevant laboratory findings, and appropriate use of resources in a data vacuum can be problematic. To address these issues, our laboratory has constructed testing panels with a tiered strategy utilizing screening assays that detect the most common causes and reflexing additional assays that assess less common etiologies. See Figure 1. Our testing algorithm panels include a rapid hemoglobin fraction monitoring test, a generic diagnostic hemoglobin electrophoresis profile, and more specific diagnostic evaluations for microcytic anemia, hereditary hemolytic anemia, methemoglobinemia and sufhemoglobinemia and erythrocytosis. Use of these testing strategies has facilitated the identification of rare and complex hemoglobin disorders from a wide variety of ethnic groups, including over 500 distinct named alpha, beta and gamma variants (of which 60+ were novel variants at the time of first detection), 99 beta thalassemia mutations and greater than 20 large deletional beta globin cluster deletion subtypes.