Last week in Discoblog, we discussed a case involving a 15-year-old boy, Alex Koehne, whose undiagnosed lymphoma was spread to four other people through the transplanting of his organs. Two of the organ recipients have died, and the other two are undergoing treatment.
So how could multiple organs carrying disease be harvested and transplanted without anyone's noticing?
Contracting a serious and sometimes lethal disease through a donated organ is a rare occurrence, but some risk exists with every transplant. In the past few years, HIV, hepatitis, tuberculosis, rabies, and West Nile virus have all reportedly been transferred to organ recipients through donations. The risk in taking organs from people who have just died is clear: The chances are higher than normal that the donor's body contained a potentially fatal disease.
The United Network for Organ Sharing (UNOS), a nonprofit organization responsible for coordinating the country's organ transplants, mandates that all organs made available for donation in the United States be screened for HIV, cancer, and certain severe infections. Such screening started after cases were reported in which HIV was transmitted via organ donation, leading the Centers for Disease Control to issue a set of guidelines to regulate transplantation of organs from donors who have engaged in "high risk" behavior. All organ donors must have their blood tested for HIV, hepatitis, syphilis, and other bacteria and viruses, while the donor's physician must check medical records or interview relatives to determine whether the donor might have cancer.
In Alex Koehne's case, a mix of policy, circumstances, and bad luck contributed to the cancer transmission. Any type of acutely spreading cancer in a donor (such as lymphoma) renders an organ ineligible for donation, but Koehne's physicians initially diagnosed him with bacterial meningitis, an extremely rare disease that does not preclude organ donation, per UNOS guidelines. Once his organs became available, they were harvested at Stony Brook University Medical Center and then, according to standard procedure for all donations in the United States, passed to a donor procurement agency, which ran the necessary tests for disease and then matched and distributed the organs according to a donor list. Koehne's cancer, a rare form of non-Hodgkin's lymphoma, was never detected by his doctors, and meningitis was not among the ailments on the checklist, so the organs were never tested for it. As a result, no one discovered that Koehne's body was meningitis-free. The presence of lymphoma was not detected until the boy's autopsy was performed, well after the organs had been transplanted.
While blood donors are screened to levels that are arguably extreme—donated blood is put through nucleic acid testing, the most thorough way to find the genomes of known pathogens—such comprehensive testing just isn't possible with organs, which need to be transplanted almost immediately so they don't begin to die. "The concepts for what [diseases] might be transmitted by blood and organs are essentially the same," says Dr. James AuBuchon, professor of pathology at Dartmouth Medical School. "The problem is how the blood supply is different from the organ supply. Most organs need to be transplanted within a few hours of being harvested."
Also at issue is the fact that blood donors are alive to answer questions for screening purposes. "But if the donor is deceased, you don’t have the luxury" of careful screening and treatment, says Catherine Garvey, the transplant coordinator at the University of Minnesota Medical Center.
To top it all off, the most commonly used tests for viruses can fail to detect what they're supposed to pick up if the tests are performed too close to the date of infection. This problem came to light in November 2007, when four patients contracted HIV and hepatitis C simultaneously after receiving organs from the same donor. Since the infection was so recent, his immune system hadn't yet produced enough antibodies to test positive for both diseases.
But the risk factors in transplants are often outweighed by the pressing need for an organ. There are currently some 97,670 people on waiting lists for organ transplants in the United States—an all-time high—and more than 6,000 people die each year while waiting. Since so many of these patients are terminally ill, the choice becomes accepting an organ that has some chance of carrying disease or else facing certain death. "We’re always weighing risk versus benefit with organ donors," says Dr. John Brems, professor of surgery and chief of intra-abdominal transplant surgery at Loyola University Health System."When it’s the end of the line [for patients awaiting transplants], often there’s no other treatment available."
Because the demand for organs so far exceeds the supply, UNOS does not prohibit transplantation of an organ from a donor with a history of cancer or high-risk sexual behavior. It does, however, require that hospitals obtain signed consent from a transplant recipient when the organ involved meets the criteria for high risk, and therefore might be diseased.
Organ procurement agencies and physicians must at minimum abide by UNOS guidelines, but they are free to adopt more stringent policies regarding screening donor tissues for infections, as well as examining patient and family histories to determine whether the donor engaged in dangerous behaviors or has been exposed to less obvious infections. "When a donor dies, the donor procurement agency does its [standard testing], and then the accepting hospital may ask for other tests to be done," says Dr. Brems."It’s up to the physicians accepting the organ to decide what their own criteria are."
Brems says most surgeons have not demanded close testing of organs when the cause of death is listed as bacterial meningitis, but after the Koehne case, he expects this to change: "If it’s a diagnosis of bacterial meningitis, we should ask, 'What is the organism that [the disease] grew out of?'" If the meningitis-causing organism can't be identified in a donor's body, says Brems, it should raise red flags for any doctor who might consider using the donor's organs.
On the whole, the system keeps the vast majority of transplant recipients safe—among the more than 230,000 major-organ transplants that took place between 1994 to 2006 nationwide, only 64 recipients developed cancer as a result of their transplant, according to UNOS. Still, the safeguards are not foolproof. "We do as much testing as humanly possible, but there’s bound to be a case where a tumor or some type of viral infection gets through that we just don’t know about and can't test for," Bremssays.