Estimated Post Transplant Survival (EPTS) Score Calculator

How does this estimated post-transplant survival (EPTS) score calculator work?

This health tool determines the numerical measure that is used in the kidney allocation system KAS. Also, EPTS is currently aimed to be performed for each candidate.

The four factors taken into account when using the EPTS score calculator are:

■ Candidate age;

■ Existence of prior solid organ transplants;

■ Candidate diagnosis of diabetes;

■ Candidate time on dialysis.

The diabetes status and the number of prior transplants are now added to the waitlist information and need to be disclosed by candidates.

EPTS scores range between 0% to 100%. A lower EPTS score indicates that the candidate is expected to benefit from more years of graft function compared to candidates with higher scores.

The Organ Procurement and Transplantation Network (OPTN) policy indicates the following formula for EPTS:

Raw EPTS = 0.047 x max (Age – 25, 0) + (-0.015) x Diabetes x max (Age – 25, 0)

+ 0.398 x Prior solid organ transplants + (-0.237) x Diabetes x Prior solid organ transplants

+ 0.315 x log(Years on dialysis + 1) + (-0.099) x Diabetes x log(Years on dialysis + 1)

+ 0.130 x (Years on dialysis = 0) + (-0.348) x Diabetes x (Years on dialysis = 0) + 1.262 x Diabetes

The above factors are transformed to suit the candidate characteristics as follows:

■ Candidate age – measured in fractional years as the number of full days between current date and candidate date of birth divided by 365.25.

■ Diabetes – binary factor, 0 if no diabetes diagnosis present and 1 if any type of diabetes is present.

■ Prior organ transplant – binary factor, 0 if no prior transplants and 1 if one or more transplants.

■ Years on dialysis – measured similar to candidate age in fractional years, which is the difference between current date or date selected by user and dialysis start date divided by 365.25.

■ If the patient is not under dialysis, then Years on dialysis is treated as 0 and “Years on dialysis = 0” is treated as 1.0 in the formula above.

The above formula was determined by estimating a multivariable Cox proportional hazards regression model.

The Raw EPTS value is then converted to the cumulative percentage based on the official EPTS Mapping Table. The raw scores observed in the reference population range between 0.01 to 3.84, rounded values.

The rule implies that candidates with scores of 20% and below are matched first with offers for kidneys from donors with KDPI scores of 20% or less.

The score does not apply in the allocation of kidneys from donors with KDPI scores that exceed 20%.

According to the above rule, EPTS is used to identify the two broad groups of patients, those with scores of 20% or below and those above 20%. In each group, the other allocation points are used to determine the waiting time, such as the CPRA or the HLA-DR matching.

The score is automatically recalculated in the system to account for changes in lapsed time or other patient factors that might change.

References

1) A Guide to Calculating and Interpreting the Estimated Post-Transplant Survival (EPTS) Score Used in the Kidney Allocation System (KAS) (2014) Organ Procurement And Transplantation Network.

2) Questions and Answers for Transplant Candidates about Kidney Allocation (2014) United Network for Organ Sharing UNOS.

3) Clayton PA, McDonald SP, Snyder JJ, Salkowski N, Chadban SJ. (2014) External validation of the estimated posttransplant survival score for allocation of deceased donor kidneys in the United States. Am J Transplant; 14(8):1922-6.

4) M. Moss, M. Gillespie, T. Sparkes, B. Ravichandran, R. Ugarte, A. Haririan. (2015) Kidney Allocation Tool of the Future: The Estimated Post-Transplant Survival (EPTS) Score. Poster Session A: Kidney Candidate Issues and Outcomes #1698.