“Mary” is a 55-year-old white, non-Hispanic woman with Medicare as her primary
insurer. She has been on peritoneal dialysis for 2 years and is scheduled for
her first kidney transplant. The primary cause of her kidney failure is
glomerulonephritis. Her body mass index is 26. (A BMI calculator requiring a
patient’s height and weight is available.) Mary’s most recent panel-reactive
antibody (PRA) score is 20%. She has no limitations in activities of daily
living (ADLs). She is hepatitis C antibody negative, and has no history of
congestive heart failure (CHF), substance abuse, atherosclerotic heart disease
(ASHD), diabetes, or chronic obstructive pulmonary disease (COPD). She does have
a history of hypertension.
Mary’s donor was a 38-year-old African American, non-Hispanic man who died of a
brain aneurysm, considered a non-traumatic death. He had no history of
hypertension or diabetes, and was also hepatitis C antibody negative. His
donation occurred after cardiac death. His terminal serum creatinine was 0.8
mg/dL. Cold ischemia time before transplant was 8 hours. The donor kidney was a
1 human leukocyte antigen (HLA) mismatch. The crossmatch was negative.
Donor-recipient cytomegalovirus (CMV) seromatching showed that both Mary and the
donor were CMV seropositive.
Entering this information in the full pretransplant model, shows that Mary has
an estimated probability of 0.241 of graft loss within 5 years. Thus, estimated
at the time of transplant, Mary has a 24% estimated risk of graft failure within
5 years. Her percentile of risk is 29, meaning that 29% of deceased-donor
transplant recipients have a lower risk of graft loss than she does, and 71%
have a higher risk (based on the observed deceased-donor kidney transplant
population in the United States between 2000 and 2006). The accompanying plot is
a distribution of the risk of graft failure in the US transplant population
between 2000 and 2006. A vertical red line marks the patient’s percentile of
risk. The area to the left of the line represents the proportion of the
population with a lower risk (probability) of graft failure than the patient,
and the area to the right the proportion with a higher risk of graft failure.
Compared with other patients, Mary has a good chance of maintaining her kidney
for 5 years.
The estimate provided by the abbreviated pretransplant model is similar: based
on the variables it considers, Mary has a 24% estimated probability of graft
failure within 5 years, placing her in the 27th percentile of the deceased-donor
transplant reference population.
Seven Days Posttransplant
The second model incorporates additional information that becomes available
within the first week posttransplant. This includes whether delayed graft
function occurred, discharge estimated glomerular filtration rate (eGFR), and
use of induction agents. Mary’s graft function was not delayed, and her
discharge eGFR was 70 mL/min/1.73 m2 as estimated by the abbreviated MDRD Study
formula. She was given prescriptions for multiple induction agents. She has no
history of smoking. Entering this additional information gives a predicted
probability of graft failure of 0.187. Thus, the probability that Mary will lose
her graft in the next 5 years is 19%, taking into account this additional
information. She is now at the 22nd percentile of risk; only 22% of the
reference transplant population has a lower risk of graft failure than she does.
All estimates provided by this model are conditional on a patient surviving at
least 7 days posttransplant.
The estimate of graft failure provided by the abbreviated model is 16%, with a
risk percentile of 9. If the information to use the full model is available, the
full model should be used.
One Year Posttransplant
Additional information is required to estimate graft survival at 1 year. This
includes eGFR at 1 year, hospitalization status during the year, BMI at 1 year,
functional status at 1 year (whether assistance in activities of daily living
was needed), presence of malignancy during the year, acute rejection, and
immunosuppressive medication compliance. Mary’s eGFR at 1 year was 55, and she
had no hospitalizations. She maintained her BMI of 26 and was compliant with her
medications. Mary experienced an acute rejection, but had no malignancies. She continued to perform activities of daily life without assistance.
predicted probability of graft loss within the remaining 4 years is 19%, placing
her in the 52nd percentile. About half of the reference population surviving to
1 year has a lower probability of graft loss, and half has a higher probability.
The area under the curve is about equal on either side of the red line.
All estimates provided by this model are conditional on the patient surviving at
least 1 year posttransplant. The estimate from the abbreviated model of 5-year
graft failure is 0.157, or 16%, placing Mary in the 33rd percentile. If the
information needed for the full model is available, the full model should be