What is GEMA?Gender-Equity model for Liver Allocation

The Gender-Equity Model for liver Allocation (GEMA) and its sodium-corrected variant (GEMA-Na) are scores designed to predict the 3-month the risk of mortality or delisting due to sickness in patients with liver cirrhosis waiting for liver transplantation¹. GEMA and GEMA-Na range from 6 to 40 points, where the higher scores are granted to patients with more advanced liver disease and increased likelihood of mortality.

FormulaGender-Equity model for Liver Allocation

GEMA and GEMA-Na were derived from generalized additive multivariate Cox regression models combining serum bilirubin, international normalized ratio (INR), Royal Free estimation of glomerular filtration rate (RFH-GFR)², and serum sodium (only for GEMA-Na). Lower and upper bounds of each parameter were defined according to their linear relationship with mortality found in the splines as follows:serum bilirubin from 20 µmol/L to 550 µmol/L; INR from 1 to 3; RFH-GFR from 20 ml/min to 100 ml/min; serum sodium 122 mmol/L to 138 mmol/L.

The equation of GEMA is expressed as follows:

GEMA = 3·777*ln(Bilirubin) + 7·883*ln(INR) – 8·306*ln(RFH-GFR) + 31·932

The equation of GEMA-Na after including the correction by serum sodium is expressed as follows:

GEMA-Na = GEMA − Na − [0·025 * GEMA * (140 − Na)] + 140

Supporting EvidencesGender-Equity model for Liver Allocation

GEMA and GEMA-Na were trained and internally validated in 7,682 patients with liver cirrhosis from the United Kingdom Transplant Registry (UKTR), which belongs to the NHS Blood and Transplant Organ Donation and Transplantation, and comprises data from all patients enlisted for liver transplantation in the United Kingdom. The models were externally validated in an independent cohort from 1,638 patients enlisted for liver transplantation in the two largest Australian liver transplant units, namely Royal Prince Alfred Hospital (Australian National Liver Transplant Unit) and Austin Hospital (Victorian Liver Transplant Unit). GEMA and GEMA-Na showed improved discrimination than MELD, MELD-Na and MELD 3·0 to predict mortality or delisting due to sickness within the first ninety days after waitlist inclusion, both in men and women, but with a more pronounced benefit in the latter group. GEMA would change the prioritization status (with two or more points) in half of liver transplant candidates, providing extra prioritization to women and to patients with ascites, which is another group historically penalized by the MELD-based prioritization system. In this study, the implementation of GEMA-Na instead of MELD-Na would potentially avoid one in nineteen deaths overall, and one in eight deaths among women¹.

ReferencesGender-Equity model for Liver Allocation

1- Rodríguez-Perálvarez M., Gómez-Orellana A., Majumdar A., et al. Development and validation of the Gender-Equity Model for liver Allocation (GEMA) to prioritize liver transplant candidates: a cohort study. Lancet Gastroenterol Hepatol. 2022 Dec 14;S2468-1253(22)00354-5. DOI: 10.1016/S2468-1253(22)00354-5Submitted for publication 2022 .Link to publication here.

2- Kalafateli M, Wickham F, Burniston M, et al. Development and validation of a mathematical equation to estimate glomerular filtration rate in cirrhosis: The royal free hospital cirrhosis glomerular filtration rate.Hepatology 2017; 65(2): 582-91.