2021 update of the 2012 ICSH Recommendations for identification, diagnostic value, and quantitation of schistocytes: Impact and revision

Hi friends, I am writing this post after a long time. Sorry about that.

Hope you are all doing well.  

The International Council for Standardization in Haematology (ICSH) published recommendations for the identification, quantitation, and diagnostic value of schistocytes in 2012.   

What was the main focus of 2012 ICSH recommendations?

Ø  Microscope evaluation method,

Ø  Specific morphologic criteria for schistocyte

Ø  Identification and percentage calculation,

Ø  Definition of a threshold value in healthy subjects 

Whats new in 2021 update ?

 It is review of the effectiveness and clinical usefulness of the ICSH 2012 recommendations based on the published literature.

Additional recommendations:

·         The study of preanalytical factors,

·         The context for reporting schistocyte percentage of clinical significance in the diagnosis of thrombotic microangiopathy (TMA) and transplant-associated TMA (TA-TMA),

·         Initial validation criteria for automated counting of red blood cell (RBC) fragments (FRCs)

 

2021 Update of the 2012 ICSH Recommendations for schistocyte identification, diagnostic value, and quantitation of schistocytes

1.Schistocytes shall be counted on Peripheral blood (PB) smears using an optical microscope (OM) at medium (x400) or high (x1000) magnification and expressed as a percentage of RBCs after counting at least 1,000 RBCs (confirmed)- Modified (high magnification included as an option)

2. A schistocyte count should be requested and carried out when a diagnosis of TMA (also named MAHAT or MAHA) caused by red cell mechanical damage is suspected, usually, although not exclusively, in the presence of thrombocytopenia- Confirmed

3. Schistocytes shall be identified based on specific positive morphological criteria:        

Ø  They are always smaller than intact red cells

Ø  Homogeneously stained in most cases

Ø  They can have the shape of fragments with sharp angles and straight borders, small crescents, helmet cells, keratocytes, or microspherocytes (only in the presence of the aforementioned RBC shapes)- Modified (possible attenuation of staining intensity in the central part is recognized as possible)

4. A schistocyte count should be considered clinically meaningful if schistocytes represent a prominent or predominant morphological RBC abnormality in the smear, and other RBC abnormalities are only slight or moderate (other than signs of erythropoietic regeneration)- Confirmed

5. A robust morphological threshold for suspecting TMA (MAHA of MAHAT) diagnosis in adult and full-term neonates is set at the percentage of schistocytes above 1%.

Nevertheless, a lack of schistocytes does not exclude a priori the diagnosis of TMA. Confirmed with an additional statement 

6. The widespread availability of automated, routine available FRC counts represents a potentially powerful tool for screening.

The absence of FRC by automated analysis can be used to exclude with high likelihood the presence of schistocytes on the blood film.

The exception is represented by samples with high MCV, which should be checked using an OM in the appropriate diagnostic setting.

Samples with a positive automated FRC count should be validated with an OM to confirm the presence of schistocytes and to enumerate them- Modified

7. Evidence-based reference values of the schistocyte percentage using the OM on PB smears are 1% or less in normal adults and full-term neonates, and 5% or less in premature babies- New, added

8. A PB smear for schistocyte count should be prepared within three hours from blood collection from samples kept at room temperature, or within eight hours from samples refrigerated at around 4°C, to avoid storage-induced morphological RBC lesions- New, added 

Figure  below shows flowchart of Schistocyte count- ICSH 2012

Int J Lab Hematol. 2012;34:107-116.


Figure below shows applications of the schistocyte count in the specific case of clinically suspect TMA. Int J Lab Hematol. 2021;00:1–8.

 


References:

1. Zini G, d'Onofrio G, N. Erber W et al. 2021 update of the 2012 ICSH Recommendations for identification, diagnostic value, and quantitation of schistocytes: Impact and revisions. Int J Lab Hematol. 2021;00:1–8.

2. Zini G, d'Onofrio G, Biggs C, et al. ICSH recommendations for identification, diagnostic value, and quantitation of schistocytes. Int J Lab Hematol. 2012;34:107-116.

                                                                                               By Dr.Priyavadhana B

 


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