Division of Nephrology in the Department of Medicine at Columbia University Irving Medical Center and the Columbia University Renal Epidemiology (CURE) Group in New York

Miko Yu, MD

New findings from a cohort study, which identified 15,602 kidneys from 8544 donors in which > 1 kidney was transplanted out of sequence, meaning it bypassed standard allocation order, is occurring earlier, more broadly, and with less justification than its stated rationale supports.

Overall, investigators observed that out-of-sequence kidney transplants reached 4,595 in 2024, nearly 1 in 4 (22.6%) of all deceased donor kidney transplants, representing an approximate 10- to 17-fold growth across all out-of-sequence categories since 2020.

Study investigators defined out-of-sequence allocation by the presence of specific operational refusal codes appearing earlier in the match run than the eventual organ acceptance code. The primary comparison group consisted of unilateral out-of-sequence cases, donors from whom 1 kidney was placed through standard in-sequence allocation and the other was placed out of sequence, allowing for a paired analysis that controls for donor-level quality factors.

Unilateral out-of-sequence transplants, the fastest-growing category, increased 17-fold and accounted for 38.2% of all out-of-sequence transplants by the end of the study period.

The median sequence number at which OPOs first switched to out-of-sequence allocation dropped from 393 in 2020 to just 28 in 2024 for unilateral out-of-sequence cases. According to investigators, this means OPOs are bypassing the standard allocation list almost immediately, well before the point at which a kidney could be considered difficult to place. The number of transplant centers receiving offers before the out-of-sequence switch also decreased, from a median of 14 in 2020 to 10 in 2024.

In 50.5% of cases, 1 kidney from a donor was placed successfully through standard allocation, while the other kidney from the same donor was placed out of sequence. This unilateral pattern directly undermines the commonly cited rationale that out-of-sequence allocation is driven by organ quality concerns or donor-related factors, since both kidneys from a donor would be expected to have comparable underlying characteristics, explains investigators.

Median KDPI scores remained relatively constant across the study period and spanned the full 1% to 100% range, further suggesting organ quality is not the primary driver of these decisions.

Recipients of unilateral out-of-sequence kidneys were disproportionately older, male, White or Asian, privately insured, more highly educated, and more likely to have received a preemptive transplant, before starting dialysis, compared with recipients of the in-sequence kidney from the same donor.

For example, 17.1% of out-of-sequence recipients had a preemptive transplant versus 10.2% of in-sequence recipients (

< .001), and 29.1% had private insurance versus 23.0% (

 < .001). These patterns suggest that the out-of-sequence pathway is consistently benefiting more socioeconomically advantaged patients.

If OPOs were bypassing standard allocation primarily to ensure efficient placement, one would expect out-of-sequence kidneys to go to the same center that accepted the paired in-sequence kidney. Instead, the vast majority (85.7%) of out-of-sequence kidneys went to a different center, and traveled significantly farther (median 171 vs. 99 nautical miles), resulting in greater cold ischemia time, not less. Only 14.8% of unilateral out-of-sequence kidneys in 2024 went to the same center that received the partner kidney.

In adjusted Cox proportional hazards models, there were no statistically significant differences in patient survival (adjusted HR, 0.84; 95% CI, 0.70–1.02; P = .08) or death-censored graft survival (adjusted HR, 0.87; 95% CI, 0.70–1.08; P = .20) between unilateral out-of-sequence and unilateral in-sequence recipients. This held across both low- and high-KDPI groups. The additional flexibility created for transplant centers by the out-of-sequence pathway thus does not appear to translate into measurable improvements in transplant outcomes, as noted by study investigators.

spoke with study investigators Miko Yu, MD, from the Division of Nephrology in the Department of Medicine at Columbia University Irving Medical Center and the Columbia University Renal Epidemiology (CURE) Group in New York, and Joel Adler, MD, MPH, an Assistant Professor of Surgery, Division of Transplant Surgery, Department of Surgery and Perioperative Care at the Dell Medical School.

HCPLive: The central design of your study compares two kidneys from the same donor: one placed in sequence, one out of sequence. When you looked at how early in the match run OPOs were triggering out-of-sequence allocation for that second kidney, what did that tell you about whether organ quality is actually what's driving these decisions?

Yu: I think our findings call into doubt whether organ quality is truly driving these decisions. In the study we also looked at the refusal reasons for these types of kidneys and it does seem that the documented reasons are not overwhelmingly due to donor or organ related concerns such as donor history, biopsy findings or organ damage/mismatch, which you might expect if that second kidney went out of sequence very early on in the match run process.

HCPLive: If donor quality isn't the primary explanation, what is? You've seen the refusal code data, you've seen how uniformly this practice expanded across all 56 OPOs and across the full KDPI spectrum in just four years, what do you think is actually happening on the ground when an OPO decides to go out of sequence?

Yu: Speaking only from a data standpoint, it’s difficult to tease out and each OPO may have its own thresholds/procedures when deciding to go out of sequence. We have also shown in our other papers that there are certain common OPO and transplant center relationships (which are not necessarily geographically close to each other) that may also factor into their decisions when opting for the out of sequence pathway.

Adler: It is a complex problem that has long been managed through largely informal solutions. OPOs and transplant centers are operating under multiple external pressures, and when those pressures are not clearly aligned with shared goals, workarounds are almost inevitable.

HCPLive: Your data show that compared to recipients of the in-sequence mate kidney, out-of-sequence recipients were significantly more likely to be privately insured, more educated, and to have received a preemptive transplant. For patients who are lower on the waitlist, who may have been on dialysis for years and are waiting their turn, what is the real-world consequence of a kidney being pulled out of sequence before it ever reaches them?

Yu: The most immediate consequence would be that these patients who may have been waiting longer are skipped over for suitable offer for a kidney. Also, when a kidney goes out of sequence, transplant centers that were bypassed may not be aware at all that they received an offer for a kidney for their patients. So without a clear mechanism for expedited allocation, it’s not hard to see how the current practice can undermine overall trust in the organ allocation system.

HCPLive: Your adjusted survival analysis found no significant difference in patient or graft outcomes between the two groups. Does that finding vindicate the practice, complicate it, or neither , and what would you need to see in future data to feel confident drawing conclusions either way?

Yu: I think when we look at all the results together—that the in-sequence kidney in this set was by definition successfully placed via the standard allocation system, that there is no significant difference in outcomes between the groups, and that there are disparities in who receives a unilateral out of sequence transplant— it certainly brings up concerns about subjectivity in current out of sequence practices.

Adler: Trust is incredibly important. Even when transplant centers and OPOs are acting in good faith, opaque or inconsistently applied practices can still undermine public trust.

HCPLive: Right now there is no standardized threshold, no required justification, and no oversight mechanism governing when an OPO can go out of sequence. Given everything your study found, what is the single most important thing that would need to change, in policy, in data collection, or in accountability, before this practice can be considered equitable?

Yu: You’re right, I think all these factors – a standardized threshold, required justification and an oversight mechanism—should be incorporated or at least taken into account when we decide on future policies for an expedited allocation pathway. That said, I’m certain what happens the ground gets to be complicated so I’ll defer to Joel on this one.

From a data standpoint, I think refusal reasons could be captured better—there is a large proportion that are categorized as “Other” which further add to the lack of transparency.

Adler: At the end of the day, there is very little debate that some form of rescue or expedited allocation pathway is needed. The challenge is deciding how to implement it, how to monitor it, and how to remain flexible as conditions change. That will only become harder with a rapidly evolving donor pool, increased federal oversight, and greater media scrutiny—but it is exactly the work the field needs to do to move forward while maintaining public trust.

Editor’s Note: Adler reports relevant disclosures with RTI International. Yu reports no relevant disclosures. 

Yu ME, Husain SA, Tucker EG, et al. Expedited Transplant Allocation Using a Paired Kidney Cohort. 

https://doi.org/10.1001/jamanetworkopen.2026.0257

Adler JT, Sharma S. Out of sequence allocation: a necessary innovation or a new inequity in transplantation? 

. Published online September 1, 2024. doi:

https://doi.org/10.1016/j.ajt.2024.09.022

Articles

Out-of-sequence deceased-donor kidney placement expanded rapidly from 2020–2024, reaching 22.6% of transplants in 2024, with unilateral out-of-sequence cases driving growth. OPOs initiated bypass increasingly early in the match run, often after few center offers, and frequently when the mate kidney was successfully placed in-sequence—undermining organ-quality rationales. KDPI distributions were stable across the spectrum. Recipients skewed toward socioeconomically advantaged profiles, while organs traveled farther with longer cold ischemia. Adjusted patient and graft outcomes were similar, elevating equity and transparency concerns.

Yu, MD, Adler, MD, share their perspectives from a cohort study on in-sequence, and out of sequence paired kidneys transplants. 