Comparison of three scoring systems for mortality risk assessment among retrieved children with meningococcal sepsis

Objective

Scoring systems assess mortality risk following intensive care unit (ICU) admission. They may also be used as risk stratification tools, both to assess severity of illness between ICUs, and as a screening tool to select patients who may benefit from novel therapies. The latter is particularly relevant to meningococcal sepsis (MNS), as mortality is highest in this condition in the first 24 hours. With the advent of paediatric retrieval teams, ICU care now essentially begins with the arrival of the team, prior to physical admission of the patient to the ICU. The effect of this practice on mortality risk assessment in MNS is unknown.

Method

Data were prospectively collected on all children with MNS retrieved by two teaching hospitals in the South-East of England over a 21-month period (December 1997–September 1999). Three scoring systems were compared: PIM, a point of care score encompassing eight variables from time of first patient contact by the retrieval team up until 1 hour after physical ICU admission; PRISM II, a physiological based system incorporating 14 variables over the first 24 hours of physical ICU admission; and pre-ICU PRISM, which includes variables collected up to 24 hours before and after ICU admission.

Results

One hundred and sixty-four children were evaluated (hospital A 62, B 102), with a crude mortality of 7.23%. Accurate data collection was verified by an intraclass correlation coefficient of >0.80 on all scoring systems for 15 randomly selected patients. Scoring performance is shown in the Table.

Table 1

Distribution of patients across mortality risk bands (< 1%, 1–5%, 5–15%, 15–30%, >30%) was similar between hospital A and B using PIM (P = 0.42) and pre-ICU PRISM (P = 0.40), but not with PRISM II (P = 0.006).

Conclusion

PIM, pre-ICU PRISM and PRISM II provide similar discrimination for mortality in retrieved children with MNS, however PIM exhibits superior calibration. In addition, distribution of patients across mortality risk bands varies between hospitals according to the scoring technique used. Scores which take into account variables collected prior to ICU admission (PIM and pre-ICU PRISM) appear to be least affected by retrieval team practice, and are thus preferable for risk stratification.