To follow or not to follow the recommendations regarding microscopic analysis of the Clinical and Laboratory Standards Institute H20-A2 to validate the criteria for blood smear review?

e read with great interest the Letter to the Editor by Grotto1 n the need to follow the Clinical and Laboratory Standards nstitute 2007 H20-A22 guidelines during microscopic analyis in reply to the study by Comar et al.3 We appreciate the omments that ensured extensive discussion on this subject. The work of Barnes et al.,4 which represents the core of he criteria for blood smear review (BSR) recommended by he International Society for Laboratory Hematology (ISLH), manates from an international consensus among 20 experts n 2002 during a conference in Indian Wells, CA, USA. In onsensus, Barnes et al.4 proposed a nine-step protocol for alidating the BSR criteria in routine laboratory practices. Step of this protocol is as follows: “Perform a slide review of all amples. Limit the reviews to only one or two senior techologists for consistency. Manual differentials should only be erformed if there is a specific need to do so (e.g., Vote out, bnormal cell-type flags, etc.)” The step-wise protocol by Barnes et al.4 does not mention he NCCLS H20-A5 as a sine qua non condition for the microcopic review of blood smears. In their work, Barnes et al.4 did ot mandate the application of the NCCLS H20-A5 guidelines, s interpreted by Grotto.1 Thus, Barnes et al.4 did not exclude he possibility of one observer counting 100 cells to validate he BSR criteria. We therefore understand that counting perormed by either one or two observers is equally acceptable. The CLSI H20-A22 (formerly NCCLS H20-A)5 is a reference ocument to evaluate hematology analyzers that perform utomated leukocyte differential counts and consider the isual leukocyte differential count as the gold standard. Most tudies that rigorously followed this guideline specifically valuated the automated leukocyte differential count and the uspect flags of the hematology analyzers.6,7 On the other and, studies evaluating sets of criteria for BSR did not necssarily follow the recommendations of the NCCLS H20-A5 or w?