ICH-ISHBT Recommendations on Synoptic Reporting of Peripheral Blood Smears (PBS)

Examination of the peripheral blood smear (PBS) is an integral component of hematologic evaluation that complements the complete blood count (CBC) and red blood cell indices in the initial assessment of most patients with suspected or established hematologic disorders. A well-prepared PBS provides critical diagnostic information regarding the formed elements of blood, often suggesting specific disease categories, guiding further investigations, and in selected conditions, prompting urgent clinical intervention. The PBS also serves additional roles: it is an important quality assurance tool for validating automated analyzer results, helps to identify spurious counts and instrument artifacts, and supports competency-based training in morphology for resident doctors and fellows. Manual microscopic review of Romanowsky-stained smears remains the reference standard for detailed morphological assessment of a blood film, particularly in complex or flagged cases. This remains true despite major advances in automated hematology analyzers and more recently, digital morphology platforms. Given the central role of the PBS and the variability that currently exists in PBS reporting formats and terminology, there is a need for harmonized, practical guidance on synoptic reporting that can be applied across diverse laboratory settings. Synoptic reporting, i.e., the use of structured headings and checklists to capture essential morphological and interpretive elements, and not missing important findings has been shown to improve report completeness, consistency, educational value, and turnaround time, while reducing typographical and omission errors. These recommendations aim to address this gap by proposing a structured, yet flexible, synoptic format for PBS reporting that aligns with the current state of knowledge and with international recommendations for morphological nomenclature and grading.