P-POSSUM Score Calculator

P-POSSUM Score Calculator for Trauma & Surgery. The Portsmouth recalibration was developed to address shortcomings of original POSSUM mortality prediction. That historical improvement does not establish present-day local accuracy. The output should not be presented as an individual prognosis, permission for surgery or a threshold for withholding treatment.

For shared guidance on choosing a tool and documenting results, read the clinical calculator workflow.

How this calculator works

The Portsmouth mortality equation uses the same completed physiological and operative totals as POSSUM but changes the regression: logit = -9.065 + 0.1692 x physiological total + 0.155 x operative total. The reported percentage is 100 / (1 + exp(-logit)). This page does not substitute a different published Portsmouth variant or claim that P-POSSUM supplies a separate morbidity model.

When to use this calculator

Use to understand the specified historical model in adult general surgery after operative findings are known. Confirm the original scoring system, completed observations and outcome definition before comparing predictions across cases. Pediatric, day-case and nonoperative assessments are outside the supported interface.

Inputs used

  • Adult general-surgery case, excluding day surgery and pediatric cases?
  • All 12 physiological and 6 operative grades finalized using the original system?
  • Completed physiological total
  • Completed operative total

Clinical interpretation

The Portsmouth recalibration was developed to address shortcomings of original POSSUM mortality prediction. That historical improvement does not establish present-day local accuracy. The output should not be presented as an individual prognosis, permission for surgery or a threshold for withholding treatment.

Worked example

With physiological total 20 and operative total 10, the logit is -9.065 + 3.384 + 1.55 = -4.131, yielding approximately 1.581% model mortality. With totals 12 and 6, the logit is -6.1046 and the estimate is approximately 0.223%. The model returns a continuous percentage without artificial decimal gaps between risk bands.

Limitations and safety notes

Integer totals are range-checked and tested for necessary arithmetic feasibility, but source components remain externally adjudicated. Different equations sometimes appear under similar labels in later literature, so record the coefficients as well as the model name. The worksheet is not reproduced and no licensing clearance, organizational endorsement or independent clinical signoff is asserted.

Frequently asked questions

Does P-POSSUM use different clinical inputs?

This specified equation uses the original POSSUM physiological and operative totals but different mortality coefficients.

Why is there no morbidity output?

P-POSSUM is a mortality recalibration. A morbidity estimate would need a separately named equation, not a relabeled number.

Is 1.581% a measured outcome?

No. It is the mathematical output for the entered totals, with historical and population-calibration limitations.

References

  • Original POSSUM identity and underlying score system. https://pubmed.ncbi.nlm.nih.gov/2021856/
  • Prytherch1998 Portsmouth paper identity, original mortality overprediction and exclusions. https://pubmed.ncbi.nlm.nih.gov/9752863/
  • Copeland source-system explanation: original physiological and operative score structure. https://jamanetwork.com/journals/jamasurgery/fullarticle/212013
  • Ngulube2019 primary prospective study Equation3: specified -9.065/.1692/.155 Portsmouth mortality coefficients. https://pmc.ncbi.nlm.nih.gov/articles/PMC6475666/
  • Primary comparison: original POSSUM morbidity is a separate equation; not relabeled as Portsmouth morbidity. https://pmc.ncbi.nlm.nih.gov/articles/PMC3215544/

Editorial review and citation methodology

Maintained by the Quick Medical Calculator Editorial Team. Content record date: September 9, 2026. A content date is not evidence of independent clinical review. Individual clinical sign-off is not recorded on this page.

  • Prefer original validation studies for scoring systems and prediction tools.
  • Use current specialty society guidance, transplant allocation policy, public health guidance, or regulator resources when they govern clinical use.
  • Include limitations and safety notes when a calculator is population-specific, context-dependent, or unsuitable as a standalone decision tool.

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