To more accurately estimate a patient's wait time for a transplant and promote transplantation for patients disadvantaged by their blood type, cPRA level or the power of their donors, the National Kidney Registry is implementing the following. We are also modifying the twin-bar graph in the NKR web Tool Box for patients (sample shown at right). These graphs will now more accurately show the projected wait for a given patient vs. others in NKR. Wait differential for a given patient ignoring vs. enforcing their preferences is also now more accurate in this graph.
Base Definitions used in this document
1.
DD - (Directed Donor) - An active donor paired to a patient
2.
Pre-RMP (Pre-Recipient Match Power) - The percentage of active donors in the NKR pool with whom a patient in need of a transplant offer is tissue-compatible. For example, if such a patient is tissue-compatible with 21 donors of an active donor pool of 235, Pre-RMP for that patient is 0.0894
(21/235).
3.
Post-RMP (Post-Recipient Match Power) - The percentage of active donors in the NKR pool with whom a
4.
patient in need of a transplant offer is both tissue- and preference-compatible. For example, if this same patient is both tissue- and preference-compatible with 17 donors of an active donor pool of 235, Post-RMP is 0.0723(17/235).
The erosion of this patient's power from preferences is
19% [1 - (0.0723/0.08940)].
DMP (Donor Match Power) - The percentage of patients in need of a transplant offer with whom the donor is both
0.10
0.09
0.08
0.07
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0.00
Pre-RMP Post-RMP tissue-compatible and preference-compatible. Assuming this patient is paired with 3 active donors, hypothetical DMP values for them would be as follows if the donation potential were are stated below: a.
Donor 1 - Can donate to 26 out of 207 patients in the NKR pool awaiting offers. Donor
1's DMP is 0.1256 (26/207). b.
Donor 2 - Can donate to 18 out of 207 patients in the NKR pool awaiting offers. Donor
2's DMP is 0.0870 (18/207). c.
Donor 3 - Can donate to 31 out of 207 patients in the NKR pool awaiting offers. Donor
3's DMP is 0.1498 (31/207).
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Extrapolated Terminology/Associated Predictive Math
From the base definitions above, the National Kidney Registry has defined additional terminology and developed steps to take to determine the approximate expected wait for a given patient. These steps produce an end result that closely tie empirical wait times for transplants arranged by the National
Kidney Registry with the characteristics of these transplanted patients. These terms and their quantitative processes are detailed below.
The left-side bar of the twin-bar graph in the NKR web Tool Box for patients shows the potential of that patient for receiving a timely transplant purely based on the patient's blood type, antibody level and directed donor complement. The right-side bar, however, shows this potential factored by the patient's preferences. Patients with no preferences have bars 2 bars of the same height while patients with preferences can have a lower height right-side bar indicating the extent to which their preferences are impeding their prognosis for a timely transplant via NKR.
1.
Term = Pre-Pref PMP a.
Start with a Pre-Pref PMP value of 0. b.
To it, add the result of the expression Pre-RMP x 100 . Pre-Pref PMP for this example is now 8.94. c.
Continue to add to Pre-Pref PMP as follows: d.
PMP with 1 donor = [(.0894 X 100) + (0.0894 X 0.1256 X 10,000)] = 112.29 e.
PMP with 2 donors = [(.0894 X 100) + (0.0894 X 0.1256 X 10,000) + (0.0894 X 0.0870
X 10,000)] = 190.07 f.
PMP with 3 donors = [(.0894 X 100) + (0.0894 X 0.1256 X 10,000) + (0.0894 X
0.0870 X 10,000)+ ((0.0894 X 0.1498 X 10,000)] = 323.99
2.
Term = Post-Pref PMP a.
Post-Pref PMP calculations are performed using the same methodology detailed above.
The difference is that Post-RMP is used in place of Pre-RMP in all expressions above.
For this patient, Post-Pref PMP is 262.10.
Since the only difference between Pre-Pref PMP and Post-Pref PMP is whether Pre-RMP or Post-RMP is used in the steps above, the samples below illustrate how the 19% Pre-RMP/Post-RMP erosion affects
Pre-Pref PMP/Post-Pref PMP for this patient. 19% erosion resulted in a 21%
Pre-Pref PMP/Post-Pref PMP erosion in this hypothetical case.
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0
Pre-RMP Post-RMP Pre-Pref PMP Post-Pref PMP
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