Clinical controls and model calibration as keys to complete blood count-based studies of pediatric fistula-in-ano

Abstract

This commentary appraises a single-center evaluation of complete blood count (CBC) markers for pediatric fistula-in-ano. We commend the pragmatic focus of this study on low-cost tests and the dual assessment of discrimination and clinical utility. To strengthen robustness and generalizability, two priorities are emphasized: First, the use of clinical controls, children with perianal symptoms but without pediatric fistula-in-ano, to avoid spectrum bias; and second rigorous calibration and validation (k-fold or temporal splits, bootstrap optimism correction, calibration intercept/slope, and Brier score), with decision curve analyses derived from validated predictions. Given rapid hematologic maturation, age should be modeled nonlinearly and CBC values should be expressed as age-specific z-scores/percentiles. Additional refinements include clear timing/indication of blood draws, appropriate correlations (Spearman or age-adjusted partials), and odds ratios per interquartile range with multicollinearity checks (variance inflation factor). These steps can translate promising CBC signals into reliable, clinically actionable evidence.

Keywords: Pediatric fistula-in-ano; Complete blood count; Neutrophil-to-lymphocyte ratio; Spectrum bias; Age standardization; Receiver operating characteristic; Decision curve analysis

Core Tip: This study evaluated widely accessible complete blood count markers in a large pediatric fistula-in-ano cohort and reported promising discrimination and decision-making ability. We highlight design and analytic refinements, clinical control selection, rigorous age handling, transparent model calibration, and validated decision curve analyses that can convert these encouraging signals into robust, generalizable evidence.