Hereditary spherocytosis diagnostic study of choice
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Overview
The diagnosis of hereditary spherocytosis can be based on physical examination, complete blood count (CBC), reticulocyte count, medical history and specific tests including eosin-5-maleimide binding (EMA) test and acidified glycerol lysis time (AGLT) test. The diagnosis can be made at any age. EMA binding test has high sensitivity and specificity for the hereditary spherocytosis. Other tests include; osmotic fragility (OF) test, pink test and ektacytometry. Gel electrophoresis analysis of erythrocyte membranes is the method of choice for diagnosis of atypical cases.
Diagnostic Criteria
- The diagnosis of hereditary spherocytosis can be based on the physical examination, complete red cell count, reticulocyte count, medical history and specific tests, preferentially, the EMA (eosin-5-maleimide binding) test and AGLT (acidified glycerol lysis time).
- The diagnosis can be made at any age, including the neonatal period from day of birth.
- The diagnostic guidelines of hereditary spherocytosis from the British Committee for Standards in hematology do not recommend any additional tests for patients with classical clinical features and laboratory data.
- The eosin-5-maleimide (EMA) binding test has high sensitivity (92–93%) and specificity (99%) for hereditary spherocytosis, although a positive test can also be obtained in patients affected by related conditions, such as congenital dyserythropoietic anemia type II (CDA II)
- Other tests, such as the osmotic fragility (OF) test, acidified glycerol lysis test (AGLT) and the pink test, exhibit lower sensitivity compared to the EMA test (68%, 61% and 91%, respectively).
- Ektacytometry is a highly sensitive test of membrane deformability.
| Clinical Parameters | pallor, splenomegaly, inconstant jaundice |
|---|---|
| Biological paraneters & erythrocyte indices | dec Hb, inc MCHC, inc %hyperdense cells, inc reticulocytes |
| Blood smear | Spherocytes (may be absent) |
| Signs of hemolysis | inc free bilirubin, dec haptoglobin, inc reticulocytes |
| Erythrocyte coombs test | negative |
| Tests | Principle/feasibility | Sensitivity/Specificity |
|---|---|---|
| Osmotic resistance | hemolysis test/routime examination | 66%/low |
| Pink test | hemolysis test/simple test time-out test <3 hours | 96%/79-94% |
| AGLT | Hemolysis test time of test >3 hours | 81%/95% |
| Ektacytometry in osmolar gradient | study of deformity of RBCs single laboratory in France test execution time:24 hours | reference exam |
| Flow cytometry | labeling of RBCs with eosin 5 maleimide/not available on routine basis test run time >48 h | Being evaluated |
- Newly diagnosed patients with a family history of hereditary spherocytosis, typical clinical features and laboratory investigations (spherocytes, raised mean corpuscular hemoglobin concentration (MCHC), increase in reticulocytes) do not require any additional tests.
- If the diagnosis is equivocal, a screening test with high predictive value for hereditary spherocytosis is helpful. The recommended screening tests are the cryohaemolysis test and EMA binding.
- Gel electrophoresis analysis of erythrocyte membranes is the method of choice for diagnosis of atypical cases.