Noutsos, Tina

Laidman AY

Survela L

Arvanitis D

Segalla R

Brown SG

Isbister GK

2021-04-13

Schistocytosis is the morphological hallmark of the microangiopathic haemolytic anaemia of thrombotic microangiopathy (TMA). Consensus guidelines for manual schistocyte quantitation are available, but limited research has evaluated them. The 2012 International Council for Standardization in Haematology (ICSH) recommends a schistocyte quantitation of 1% as a robust cut-off for significance, with the quantitation including helmet, crescent, triangle and keratocyte poikilocytes; and microspherocytes only in the presence of helmets, crescents/triangles, and keratocytes. We aimed to evaluate the relative contribution of these different poikilocytes to schistocyte counting; compare the ICSH method with our proposed method which counts only cells most specific for red cell fragmentation (helmet, crescent and triangular schistocytes); and evaluate inter- and intra-observer agreement. Blood films were sourced from the Australian Snakebite Project, including non-envenomed and envenomed cases, with and without TMA. In blood films across the range of schistocytosis, the predominant poikilocytes present were helmets and crescents. Triangles, keratocytes and microspherocytes were typically only present when ICSH schistocyte count was >1%. With results dichotomised as <1.0% or ≥1.0%, our proposed new method versus the ICSH method showed almost perfect agreement [observed agreement 95%, Cohen's kappa (κ)=0.84, SE 0.04, 95% CI 0.76-0.92, p<0.005]. Inter-observer strength of agreement for our method was moderate (Fleiss' κ for comparisons between three non-unique microscopists κ=0.50, SE 0.05, 95% CI 0.41-0.59, p<0.005). Intra-observer reproducibility assessed in two microscopists ranged from substantial (Cohen's κ=0.71, SE 0.08, 95% CI 0.55-0.86, p<0.005) to borderline almost perfect agreement (Cohen's κ=0.81, SE 0.07, 95% CI 0.68-0.93, p<0.005). Schistocyte quantitation using our new method is simpler than the 2012 ICSH method and had almost perfect agreement. Our finding of moderate inter-observer agreement in quantitating helmet, triangle and crescent schistocytes is applicable to both the ICSH and our newly proposed method. This finding underscores the importance of clinicopathological correlation and repeated examinations in the context of a clinically suspected TMA.

Menzies School of Health Research, Charles Darwin University, Darwin, NT, Australia; College of Medicine and Public Health, Flinders University, Adelaide, SA, Australia; Division of Medicine, Royal Darwin Hospital, Darwin, NT, Australia. Electronic address: tina.noutsos@flinders.edu.au.

Division of Medicine, Royal Darwin Hospital, Darwin, NT, Australia.

Royal North Shore Hospital, St Leonards, NSW, Australia; Westmead Hospital, Westmead, NSW, Australia.

Westmead Hospital, Westmead, NSW, Australia.

Centre for Clinical Research in Emergency Medicine, University of Western Australia, Perth, WA, Australia; Aeromedical and Medical Retrieval Division, Ambulance Tasmania, Hobart, Tas, Australia.

Clinical Toxicology Research Group, University of Newcastle, Newcastle, NSW, Australia.

Pathology. 2021 Apr 13:S0031-3025(21)00087-8. doi: 10.1016/j.pathol.2021.01.008.

https://pubmed.ncbi.nlm.nih.gov/33863504/?otool=iaurydwlib

https://hdl.handle.net/10137/11746

An evaluation of existing manual blood film schistocyte quantitation guidelines and a new proposed method.

Journal Article

Publication