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Does horizontal and vertical thinking provide the right angle of approach to complex problems?
  1. Philip D Welsby1
  1. Retired, Edinburgh, UK
  1. Correspondence to Philip D Welsby, Retired, Edinburgh, UK; Philipwelsby{at}

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Taro Shimizu presented a new diagnostic thinking forcing strategy,1 not previously explicitly defined, comprising Horizontal Tracing (HTr) based on identifying primary diagnoses (PDs) that allows simultaneous identification of other possible associated conditions, using what are essentially simple flowcharts, and Vertical Tracing (VTr) that entails searching for aetiological diagnoses underlying the PD. The scheme outlined is a coherent way of delivering a full diagnosis that must include anatomical, physiological and aetiological elements.

There are five considerations. First, in clinical medicine, uncertainty and complexity abound ‘cognitive noise’ and errors made initially in PDs may result in amplified errors. Humans cannot adequately cope with such complexities because they overwhelm …

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  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Provenance and peer review Commissioned; internally peer reviewed.

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