External validation of a modified model of Acute Physiology and Chronic Health Evaluation (APACHE) II for orthotopic liver transplant patients

Yaseen Arabi,Kenneth Wood,Abdulmajeed Al-Abdulkareem,Abudullah AL Shimemeri,Radoslaw Goraj,Munci Kalayoglu,Adnan Abbasi

doi:10.1186/cc1497

Abstract

IntroductionThe purpose of the study was to validate the newly derived postoperative orthotopic liver transplantation (OLTX)-specific diagnostic weight for the Acute Physiology and Chronic Health Evaluation (APACHE) II mortality prediction system in independent databases.MethodsMedical records of 174 liver transplantation patients admitted postoperatively to the adult intensive care units at King Fahad National Guard Hospital and the University of Wisconsin were reviewed, and data on age, sex, the underlying liver disease, APACHE II scores and the hospital outcome were collected. Predicted mortality was calculated using: 1) the original APACHE II diagnostic weight of postoperative other gastrointestinal surgery and 2) the newly derived OLTX-specific diagnostic category weight. Standardized mortality ratio and 95% confidence intervals were calculated. Calibration was evaluated with the Hosmer–Lemeshow goodness-of-fit C-statistic. Discrimination was tested by 2 × 2 classification matrices and by computing the areas under the receiver operating characteristic curves. Patient characteristics and outcome data were compared between the two hospitals.ResultsAPACHE II significantly overestimated mortality when the original diagnostic weight was used, but provided a closer estimate of mortality with the OTLX-specific diagnostic weight. The C-statistic analysis showed better calibration for the new approach; discrimination was also improved. The performances of the prediction systems were similar in the two hospitals. The new model provided more accurate estimates of hospital mortality in each hospital.DiscussionAPACHE II provided an accurate estimate of mortality in liver transplant patients when the OLTX-specific diagnostic weight was used. With the new model, APACHE II can be used as a valid mortality prediction system in this group of patients.

Highlights

The purpose of the study was to validate the newly derived postoperative orthotopic liver transplantation (OLTX)-specific diagnostic weight for the Acute Physiology and Chronic Health Evaluation (APACHE) II mortality prediction system in independent databases
When the original diagnostic weight was used, APACHE II significantly overestimated mortality
When the new diagnostic weight was used, the system provided a closer estimate of mortality

Summary

Introduction

The purpose of the study was to validate the newly derived postoperative orthotopic liver transplantation (OLTX)-specific diagnostic weight for the Acute Physiology and Chronic Health Evaluation (APACHE) II mortality prediction system in independent databases. Systems for predicting the severity of illness and mortality, such as the Acute Physiology and Chronic Health Evaluation (APACHE) II system, are attractive options for this group because they rely on data collected soon after admission to the intensive care unit (ICU), which is likely to reflect preoperative, intra-operative and postoperative contributions. The multiple logistic regression equations were based on data collected on 5050 medical and surgical patients admitted to the ICU in 13 tertiary medical centers in the USA. This outcome prediction system has been used to evaluate and compare the performance of ICUs in different hospitals and countries. In addition to general ICU patients, APACHE II has been studied in specific groups of patients such as those with trauma [6], sepsis [7], and cirrhosis [8]

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