Methods to decrease variability in histological scoring in placentas from a cohort of preterm infants

Objective: Reliable semiquantitative assessment of histological placental acute inflammation is problematic, even among experts. Tissue samples in histology slides often show variability in the extent and location of neutrophil infiltrates. We sought to determine whether the variability in pathologists' scoring of neutrophil infiltrates in the placenta could be reduced by the use of 'regions of interest' (ROIs) that break the sample into smaller components. Design: ROIs were identified within stained H&E slides from a cohort of 56 women. ROIs were scored using a semiquantitative scale (0-4) for the average number of neutrophils by at least two independent raters. Setting: Preterm singleton births at Yale New Haven Hospital. Participants: This study used stained H&E placental slides from a cohort of 56 women with singleton pregnancies who had a clinically indicated amniocentesis within 24 hours of delivery. Primary and secondary outcome measures: Interrater agreement was assessed with the intraclass correlation coefficient (ICC) and log-linear regression. Predictive validity was assessed using amniotic fluid protein profile scores (neutrophil defensin-2, neutrophil defensin-1, calgranulin C and calgranulin A). Results: Excellent agreement by the ICC was found for the average neutrophil scores within a region of interest. Log-linear analyses suggest that even where there is disagreement, responses are positively associated along the diagonal. There was also strong evidence of predictive validity comparing pathologists' scores with amniotic fluid protein profile scores. Conclusions: Agreement among observers of semiquantitative neutrophil scoring through the use of digitised ROIs was demonstrated to be feasible with high reliability and validity.