Inclusion Criteria:

* Cohort 1

* Capable and willing to provide informed consent for participation in the study.
* Diagnosis of myelodysplastic syndrome (MDS) or myelodysplastic/myeloproliferative neoplasm (MDS/MPN syndrome) according to 2016 World Health Organization (WHO) classification system.
* Anemia secondary to underlying MDS or MDS/MPN syndrome, defined as a hemoglobin \<11.0 g/dL measured within 30 days of study enrollment. Anemia should not be related to nutritional deficiency (such as iron, cobalamin, folate, or copper deficiencies), peripheral immune or non-immune hemolysis, or renal disease, in the opinion of the investigator.
* Age \>18 years.
* Cohort 2

* Capable and willing to provide informed consent for participation in the study.
* Diagnosis of a clonal myeloid neoplasm, such as MDS, MDS/MPN syndrome, myeloproliferative neoplasm (MPN), acute myeloid leukemia (AML), clonal cytopenia of undetermined significance (CCUS), or other clonal myeloid neoplasm according to 2016 World Health Organization (WHO) classification system.
* A diagnosis of an otherwise unexplained Coombs-negative non-immune hemolytic anemia, according to the clinical judgement of the investigator. Some form of objective laboratory evidence must be present, including one or more of the following: negative direct antiglobulin (Coombs) test, reduced haptoglobin, elevated indirect bilirubin, elevated lactate dehydrogenase, elevated aspartate aminotransferase, or compatible findings on peripheral blood film. Results of all of these tests are not required to satisfy this criterion.
* Age \>18 years.

Exclusion Criteria:

* Cohort 1

* Receipt of red cell transfusion within 60 days of study enrollment.
* Have a known untreated nutritional anemia or acquired disorder resulting in hemolysis, such as paroxysmal nocturnal hemoglobinuria (PNH). A known hereditary anemia (such as thalassemia trait) is not exclusionary if the patient's baseline hemoglobin has worsened significantly (in the opinion of the investigator) after development and diagnosis of MDS.
* Cohort 2

* Have a known hereditary anemic disorder, such as thalassemia, sickle cell disease, or hereditary enzyme deficiency, with the exception of hereditary X-linked glucose-6-phosphate dehydrogenase deficiency known not to cause chronic baseline hemolysis. Testing for these diagnoses is not required unless deemed clinically necessary.
* Have a known untreated nutritional anemia or acquired disorder resulting in hemolysis, such as paroxysmal nocturnal hemoglobinuria (PNH).