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Prioritizing a high posterior probability threshold leading to low error rate over high classification accuracy: the validity of MorphoPASSE software for cranial morphological sex estimation in a contemporary population

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Abstract

An increasing number of software tools can be used in forensic anthropology to estimate a biological profile, but further studies in other populations are required for more robust validation. The present study aimed to evaluate the validity of MorphoPASSE software for sex estimation from sexually dimorphic cranial traits recorded on 3D CT models (n = 180) from three populations samples (Czech, French, and Egyptian). Two independent observers performed scoring of 4 cranial traits (2 of them bilateral) in each population sample of 30 males and 30 females. The accuracy of sex estimation using traditional posterior probability threshold (pp = 0.5) ranged from 85.6% to 88.3% and overall classification error from 14.4% to 11.7% for both observers, and corresponds to the previously published values of the method. The MorphoPASSE method is also affected by the subjectivity of the observers, as both observers show agreement in sex assignment in 83.9% of cases, regardless of the accuracy of the estimates. Applying a higher posterior probability threshold (pp 0.95) provided classification accuracy of 97.9% and 93.3% of individuals (for observer A and B respectively), minimizing the risk of error to 2.1% and 6.7%, respectively. However, sex estimation can only be applied to 54% and 66% of individuals, respectively. Our results demonstrate the validity of the MorphoPASSE software for cranial sex estimation outside the reference population. However, the achieved classification success is accompanied by a high risk of errors, the reduction of which is only possible by increasing the posterior probability threshold.

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The datasets generated during and/or analyzed during the current study are available from the corresponding author upon reasonable request.

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Authors and Affiliations

  1. Department of Anthropology and Human Genetics, Faculty of Science, Charles University, Viničná 7, 128 44, Prague 2, Czech Republic

    Anežka Pilmann Kotěrová, Šárka Bejdová, Rebeka Rmoutilová, Jana Velemínská & Jaroslav Brůžek

  2. UMR 5199 – PACEA, Université de Bordeaux, Bâtiment B2, Allée Geoffroy Saint Hilaire, CS 50023, 33615, Pessac Cedex, France

    Frédéric Santos & Jaroslav Brůžek

  3. Department of Forensic Medicine and Clinical Toxicology, Faculty of Medicine, Alexandria University, Alexandria, 21568, Egypt

    MennattAllah Hassan Attia

  4. Department of Radiology, Faculty of Medicine, Alexandria University, Alexandria, Egypt

    Ahmed Habiba

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  1. Anežka Pilmann Kotěrová
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Correspondence to Anežka Pilmann Kotěrová.

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The use of CT was approved by the ethical board of the Faculty of Science, Charles University in Prague, Czech Republic, the Medical Faculty, Aix-Marseille University, France, and the Alexandria Faculty of Medicine Ethical Committee in Egypt (ethical approval serial number 0306062, IRB NO: 00012098 -FWA NO: 00018699).

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Pilmann Kotěrová, A., Santos, F., Bejdová, Š. et al. Prioritizing a high posterior probability threshold leading to low error rate over high classification accuracy: the validity of MorphoPASSE software for cranial morphological sex estimation in a contemporary population. Int J Legal Med (2024). https://doi.org/10.1007/s00414-024-03215-1

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