Researchers Zap Industry-Funded Studies on Stun Gun Safety

May 16, 2011
Christine Young, Fair Warning

Plenty of studies suggest that the stun guns that police sometimes use to subdue suspects are safe. But a new analysis questions the credibility of at least some of that research.

That analysis, by cardiologists at the University of California, San Francisco, was based on a review of 50 published studies on Taser guns. According to a university news release, 23 of the studies either were financed by Taser International Inc., the leading maker of electrical stun guns, or were written by an author affiliated with the company.

The other 27 studies were conducted by independent researchers.

In findings delivered at a conference this month, the UC researchers said all but one of the manufacturer-backed studies said stun guns were either not harmful or not likely to be harmful. Yet among the independent assessments, only slightly more than half — 15 of the 27 studies — came to similar conclusions.

“When you look at the research, you find out a lot of the articles that are touted by police departments are funded by the company,” Dr. Byron Lee, an associate professor at the university and senior author of the study, told The New York Times.

The potential hazards of stun guns were demonstrated last week when a 43-year-old man died after being stun-gunned by deputies in Southern California’s San Bernardino County, according to the Los Angeles Times.

Deputies tried to stop the man after he allegedly ran a stop sign. Cindy Bachman, a sheriff’s department spokeswoman, said the suspect, who had no prior criminal record, had become “combative and uncooperative.” The victim’s father said he was told that his son was Tasered about eight times.

In 2009, five men in San Bernardino County and neighboring Riverside County died after being shot with stun guns, Inland News Today reports. In response, Taser issued an advisory that aiming the device at a suspect’s chest could cause an “adverse cardiac arrest.”

Truth, Not Tasers, a website that tracks stun guns deaths, says 19 people have died so far this year, and 65 were killed last year, in U.S. stun gun incidents.

UCSF doctor questions Taser studies

UCSF Heart Doctors Uncover Significant Bias in Taser® Safety Studies

OfficialTASER on Twitter:

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@phxbizjournal #TASER studies repeated by independent orgs (UCSD & Wake Forest) validated results & directly refute any claim of bias.
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@ucsf #TASER studies repeated by independent orgs (UCSD & Wake Forest, etc) validated our results & directly refute any claim of bias.
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Of the 50 articles studied, 23 were funded by TASER International, Inc. or written by an author affiliated with the company. Nearly all (96 percent) of the TASER-supported articles concluded the devices were either “unlikely harmful” (26 percent) or “not harmful” (70 percent). In contrast, of the 27 studies not affiliated with TASER International, 55 percent found that TASERs are either “unlikely harmful” (29 percent) or “not harmful” (26 percent).

Louise Vance
louise.vance@ucsf.edu
415-502-6397

May 6, 2011

The ongoing controversy surrounding the safety of using TASER® electrical stun guns took a new turn today when a team of cardiologists at the University of California, San Francisco announced findings suggesting that much of the current TASER®-related safety research may be biased due to ties to the devices’ manufacturer, TASER International, Inc.

In a research abstract presented at the Heart Rhythm Society’s 32nd Annual Scientific Sessions at the Moscone Center in San Francisco, study author Peyman N. Azadani, MD, research associate at UCSF’s Department of Medicine, Division of Cardiac Electrophysiology, and senior author Byron K. Lee, MD, associate professor of medicine in UCSF’s cardiology division, set out to gauge the accuracy of 50 published studies on the potential dangers of using TASER® products. Lee directs the Electrophysiology Laboratories and Clinics in UCSF’s Cardiology Division, and first published research on the safety of law enforcement use of TASERs in 2009.

The new study’s authors report that among the product safety studies they analyzed, the likelihood of a study concluding TASER® devices are safe was 75 percent higher when the studies were either funded by the manufacturer or written by authors affiliated with the company, than when studies were conducted independently.

Azadani, Lee and three colleagues divided TASER® safety study outcomes into four categories: harmful, probably harmful, unlikely harmful and not harmful. Of the 50 articles studied, 23 were funded by TASER International, Inc. or written by an author affiliated with the company. Nearly all (96 percent) of the TASER-supported articles concluded the devices were either “unlikely harmful” (26 percent) or “not harmful” (70 percent). In contrast, of the 27 studies not affiliated with TASER International, 55 percent found that TASERs are either “unlikely harmful” (29 percent) or “not harmful” (26 percent).

TASERs are the most popular brand of electrical stun guns, used primarily by law enforcement agencies to incapacitate combative suspects. The devices, also marketed for home use, deliver electrical pulses that stimulate the nervous system and cause involuntary muscle contractions. Advocates of using such conductive energy devices, or CEDs, say that they are effective and cause only temporary physical symptoms. Critics and scientists have raised concerns about the potential dangers of using TASER® devices, particularly on pregnant women, the elderly and very young, and individuals with underlying medical conditions.

The UCSF-led research findings have been submitted for publication but are not yet published in a peer-reviewed scientific journal. The study’s other authors are Zian H. Tseng, MD and Gregory M. Marcus, MD, both assistant professors of medicine at UCSF School of Medicine, Division of Cardiology, and Simon Ermakov, BA. The scientists conclude that when reading about TASERs, the public should consider the funding source and author affiliation when evaluating an article’s safety conclusions.

UCSF is a leading university dedicated to promoting health worldwide through advanced biomedical research, graduate-level education in the life sciences and health professions, and excellence in patient care.

San Francisco police chief Gascon gives up on arming officers with tasers

March 5, 2010
Jaxon Van Derbeken, San Francisco Chronicle

SAN FRANCISCO -- A day after the San Francisco Police Commission rejected his proposal to arm officers with Tasers, Chief George Gascón said Thursday he is giving up his push for the devices that he billed as a possible alternative to the use of deadly force.

The commission voted 4-3 just before midnight Wednesday not to give Gascón the go-ahead to develop guidelines under which officers could use the electronic stun guns, which would have been a first step toward adopting Tasers.

Opponents pointed to studies suggesting that the devices can kill people with heart conditions or even those who are otherwise healthy, and were skeptical of police promises that officers' use of Tasers would be sharply restricted.

In an interview Thursday, Gascón said he was "extremely disappointed" by the vote and would no longer press the matter.

"The majority of the commission has spoken loud and clear on this issue - they don't want to address it," Gascón said. "So we're going to just back off from it for the time being."

Chief researched incidents

Gascón, who had cited a study finding that as many as a third of 15 officer-involved shootings in a five-year period in San Francisco could have been avoided with Tasers, added: "Hopefully, there will not be any unfortunate incidents."

The Taser proposal was the first major policy initiative that Gascón had brought before the commission, which hired him on a unanimous vote last year on the recommendation of Mayor Gavin Newsom. Some of the commissioners who voted against the plan made it clear they felt the chief had overstepped his authority by not letting the panel be involved in vetting his idea.

Commissioner Petra DeJesus, one of three panel members appointed by the Board of Supervisors, said she refused to be a "rubber stamp" for the Police Department and Gascón, whom she accused of trying to circumvent a full review on whether the devices were safe to use on suspects.

DeJesus and the other commissioners appointed by the supervisors, Vincent Pan and Jim Hammer, joined Newsom appointee Yvonne Lee in rejecting Tasers.

Three backers on panel

All three votes in favor were cast by Newsom's other appointees - panel President Joe Marshall and Commissioners Thomas Mazzucco and David Onek.

During Wednesday's five-hour meeting, Gascón cited research by the Police Executive Research Forum think tank that found that police departments that adopted Tasers had dramatically lower rates of shootings and injuries than other departments.

But the commission also heard from two UCSF cardiology professors whose study of 50 police departments in California found that officer-involved shootings and deaths of suspects actually spiked during the first year of Taser deployment.

Other critics noted that roughly 400 people in the United States have died since 2001 after being hit with Tasers.

Hammer - who had attended a news conference Gascón held last week to push for Tasers - said Wednesday night that the UCSF study data had changed his mind.

He said almost half the department's 2,000 officers have not yet undergone training for dealing with mentally ill suspects, who he said were more likely to resist police orders and thus be hit with Tasers. Until those officers are trained, he said, he won't "rush into" adopting Tasers.

'He is the CEO'

Marshall, the panel's president, said he was bewildered by the vote.

"We brought him in there," Marshall said of Gascón. "He is the CEO, he runs the organization. He should be given the opportunity to try things."

Police union President Gary Delagnes called the commission's vote "political correctness run amok. Four people on the Police Commission obviously think that they know more than the experts in the field, more than the police chief.

"The next time someone in the city is killed, and it could have been prevented because of a use of Taser, the blood is on their hands," Delagnes said.

Gascón has cautioned that Tasers could not be used in lieu of guns in all situations, but he said he could easily envision situations where officers would use a Taser if given the choice. He said the commission's vote eliminated that possibility.

"What we're saying, is, 'You know what? We would rather you use a firearm and forget about the possibility of having this other option,' " Gascón said.

"I don't believe the commission is doing this to send any kind of personal message to me," he said. "But I think they are sending a message to the public and the organization at large. I'm not really sure what that message is.

"In the meantime, we've still got officers encountering situations out there with a tool bag that lacks all the tools that are available today."

Cardiologist offers police three tips for reducing taser deaths

February 24, 2009
By Carlito Pablo, Georgia Strait

A U.S.-based cardiologist who provided expert testimony last year at the inquiry into the taser-related death of Polish immigrant Robert Dziekanski has some recommendations for police that could help lower the risk of killing someone with a stun gun.

However, Dr. Zian Tseng, an assistant professor in medicine at the University of California at San Francisco, stressed that police officers should be made aware of the potentially fatal consequences of using tasers.

“If you knew that the taser could potentially kill, obviously you wouldn’t pull it out as quickly as if you thought it was completely safe,” Tseng said in a phone interview with the Straight.

Tseng said that the high-voltage weapon has “almost zero” effect on the heart if it is not fired on a person’s chest area.

“The vector over the heart is very important,” he said. “So one practical recommendation would be is if it’s possible to avoid tasering the chest.”

Tseng said that it has been shown that the more times a police officer pulls the trigger of a taser, the longer that electrical pulses course through the recipient’s body. This increases the risk of the pulses “capturing the heart and affecting the heart rhythm”, he said.

Therefore, his second recommendation is that police officers should ease up on the trigger.

Tseng’s third recommendation is for police squads carrying tasers to be equipped with automated external defibrillators that can be used to revive a person who has been shocked with the weapon and suffered a cardiac arrest.

“These are very easy to obtain, they’re relatively inexpensive, and, in my opinion, if a police agency is using the taser, they should have the defibrillator available in case a cardiac arrest happens,” Tseng said.

Tseng added that these devices, which are about the size of a laptop computer, cost about $1,000 to $1,200.

Police agencies not much moved by UCSF Taser study

February 3, 2009
By Robert Salonga, Contra Costa Times

A UC San Francisco study cautioning about the dangers of police use of Tasers has been coolly received by Contra Costa law enforcement authorities who say the device has bolstered the safety of both officers and suspects in violent situations.

The Taser has been proffered as a nonlethal alternative to firearms. But the statistical study found that the devices did not significantly increase officer safety or decrease officer-involved shooting deaths in the first year of use.

The UCSF research team conceded important limitations of the study, particularly the size of the data pool. Fifty of 126 California law enforcement agencies sent complete data to researchers, and the country's 10 largest cities were contacted but did not respond. Researchers, who estimate that Tasers are used by 12,000 law enforcement, military and correctional agencies worldwide, declined to comment specifically on which agencies responded.

The other key limitation of the study is that in the case of non-firearm in-custody deaths, it is not clear how many involved the use of a Taser. At best, the figures can be associated only with the availability of Tasers to officers.

"Since this is an observational study, it's hard to make definitive conclusions. But it definitely raises questions about its safety," said Byron Lee, author of the study and an assistant clinical professor in cardiology.

Except for the Sheriff's Office, law enforcement officers on patrol in Contra Costa County use a model of the Taser, the most popular brand of electric stun gun that shoots probes with electric current to briefly incapacitate a person. The Sheriff's Office only uses Tasers in county jails.

Local law enforcement agencies agreed that Taser use carries risks, but no more than any other means of force. But they said the study seemed to downplay the safety benefits Tasers provide for officers and suspects.

"Prior to it coming along, there was ... a big gap between intermediate force options like batons and pepper spray, and lethal force," said Concord police Sgt. Dave Hughes, who oversees his department's Taser training.

Three of the police agencies interviewed by the Times — Antioch, Concord and the Sheriff's Office — have not had Tasers in wide circulation long enough for the study. Brentwood police Lt. Tom Hansen said his department has had Tasers in place for about five years, but said he wasn't aware of his department being contacted by researchers.

The study, posted online in late January and set for publication in the American Journal of Cardiology, compared non-firearm suspect deaths, firearm deaths, and officer injuries in the five years before Taser deployment and five years after. Cardiologists led the study in part because Tasers have been demonstrated to cause rapid irregular heartbeat, and adrenaline from a struggle and multiple shocks near the heart can make a person more susceptible to death or injury.

In the first of year of Taser use, study data showed a sixfold increase in non-firearm, in-custody deaths of police suspects, from 0.93 per 100,000 arrests to 5.96. In the same period, the study found the frequency of suspect deaths involving the use of a firearm more than doubled from 6.66 per 100,000 arrests to 15.1. Researchers did not get comparable data to track officer injuries in the same period, but observed no significant change linked to Taser use.

But after the first year — which varies, though police departments started adopting Tasers in the late 1990s — the study suggested that police adjusted their use and deaths and injuries returned to levels before Taser implementation.

Hughes offered statistics from his own department refuting the study's observations. In Concord, figures from 2006 — the first full year Tasers were used — show a 21 percent decrease from 2005 in "use of force" events, which include police dogs, physical restraint, batons and pepper spray. Those figures include one on-duty firearm discharge in 2005 and none the following year.

Officer injuries in 2006 decreased 35 percent from 2005, from 26 to 17. Hughes said that can be largely attributed to an increase in Taser uses, with 47 recorded discharges in 2006, up from 17 in 2005, when officers also used other forms of stun guns.

There have been no recorded in-custody deaths in Contra Costa County directly linked to Taser use. In one instance, however, a Taser was one of several measures used on Uriah Dach, a 26-year-old mentally ill man who died after a violent struggle with police April 22 at a Richmond boardinghouse. Dach had ripped out the Taser prods police used on him during the fracas.

Local police agencies said officers undergo routine Taser training. Antioch police Sgt. Tammany Brooks, whose department started using Tasers in 2006, oversees a 10-hour training session on the device. Officers must recertify each year.

The training covers areas such as the optimal spots on the body to aim Taser shots that incapacitate without causing injury. That includes larger muscles, such as the back and legs. Officers also learn to stand far enough from the target — between 10 feet and 15 feet — to ensure the Taser probes create a circuit large enough to stop someone.

When used properly, Hughes said, suspects who are Tasered avoid serious injury.

Researcher Lee stressed that the study does not advocate for the abandonment of Tasers. Its larger purpose is to show that Tasers may not be completely safe and need more third-party study.

"It's definitely better than shooting somebody," he said, but "there may be some inherent dangers and more research needs to be done to find out how safe or unsafe the device is."

U.S. study raises more questions about stun gun safety

January 25, 2009
CBC News

The Taser stun gun has been advertised and sold as a police tool that can decrease the number of suspect shooting deaths and officer injuries, but a new study suggests its use does not reduce the number of people who die in custody.

The study was conducted by researchers at the University of California San Francisco. They surveyed U.S. city police departments for cases of in-custody sudden deaths in the absence of lethal force in the five years before they started using Taser stun guns and the same period after deployment began. Fifty of the 84 departments approached were able to provide data.

The research group found a sharp increase in the rate of in-custody sudden death in the first full year of Taser deployment compared with the average rate in the five years before the stun guns were used.

"A little bit to our surprise we found a statistically significant six-fold increase in the in-custody sudden death rate in the first full year of Taser deployment, and that rate then declined down near baseline in years two to five," said one of the researchers, cardiologist Zian Tseng.

Tseng testified last May at the Braidwood inquiry, which is looking into the death of a Polish immigrant Robert Dziekanski at Vancouver International Airport in October 2007.

Over the entire reporting period, researchers found the average rate of 1.57 sudden deaths per 100,000 arrests in the 50 cities. In the first full year after stun guns were deployed, the rate was 5.96 per 100,000 arrests, a 6.4-fold increase over the predeployment period.

The study showed that in the first complete year after deployment, the rate of deaths caused by officers using firearms remained high at 15.1 per 100,000 arrests, a 2.3-fold increase over the predeployment period. In years two to five after deployment, the rate of lethal force deaths decreased to 9.1 per 100,000 arrests.

Officers adjusted use, researcher believes

Tseng said his team concluded that police likely changed the way they used the Taser after the first year and that accounted for the drop in sudden in-custody deaths. He thinks the findings point to the importance of stringent policies for Taser use.

Tseng told Vancouver's Braidwood inquiry that a normal healthy person could die after a jolt from the stun gun if the shock went into the chest during a vulnerable point in the heart beat.

The U.S. researchers acknowledge their study is "purely observational" and has limitations because they did not ask police for details about the reported in-custody deaths and did not ask whether the Taser had actually been applied in those incidents, meaning the weapon was used only in a subset of these deaths.

However, they said, other investigators have suggested that stun guns may cause sudden death by increasing the risk of excited delirium, a much-debated condition in which sudden death occurs after a violent struggle.

Canadian physicians concerned

The Canadian Medical Association has raised concerns in the past about police departments relying on the manufacturer's claims of safety, and has called on police departments to open their databases to researchers.

Dr. Matthew Stanbrook, deputy editor for science at the CMA's Journal, thinks the U.S. study is a good first step toward building a body of work about real-life stun gun use.

"Greater societal pressure needs to be put on agencies on this to release that information for the public good because people are asking serious questions about this," he said.

Taser International, which is based on Scottsdale, Ariz., has been selling the most popular brand of stun gun to police departments in North America since 2001. The company has data on its website that it says shows the number of injuries to police officers has dropped dramatically since the introduction of the stun gun.

The San Francisco study found no change in the injury rate to officers. However, researchers noted in their report that the 10 largest U.S cities where stun guns are used most frequently refused to release their Taser data for the study.

UCSF study raises doubts about stun gun safety

January 24, 2009
Elizabeth Fernandez, San Francisco Chronicle

The number of in-custody sudden deaths rose dramatically during the first year California law enforcement agencies began using stun guns, raising questions about the safety of the devices, according to a new study at UCSF.

The electronic weapons are intended to be a nonlethal alternative to the gun.

"Tasers are not as safe as thought," said Dr. Byron Lee, one of the cardiologists involved in studying the death rate related to Tasers, the most widely used stun gun. "And if they are used, they should be used with caution."

The researchers analyzed sudden death data from 50 law enforcement agencies in the state that use Tasers. They compared the death rate pre- and post-Taser deployment - analyzing data for five years before each agency began using Tasers and five years afterward.

They found a sixfold increase in sudden deaths during the first year of Taser use - amounting to nearly 6 deaths per 100,000 arrests.

"I didn't expect what we found," said Lee. "I thought we would find no difference in the rate of sudden death. But there was a rather dramatic rise."

After the first year, the rate of sudden deaths dropped down to nearly pre-Taser levels, suggesting that police and others in law enforcement altered the way they were using the devices to make them less lethal.

"Sudden deaths are extremely rare events, but it is important to look into why these events happen and whether law enforcement agencies are fully informed of the real-world risks," Lee said.

California does not have a statewide training standard for stun guns, which have been used in the state for decades.

"The manufacturer provides introductory training, then law enforcement agencies do supplemental training," said Robert Stresak, a spokesman for the California Commission on Peace Officer Standards and Training, which sets minimum training standards. "It's on an agency by agency basis. The content of the course could vary widely as to what is taught."

Tasers, known as "conducted energy" devices, send out high-frequency pulses which can cause a very rapid, dangerous heart rhythm, said senior author Dr. Zian H. Tseng, an assistant clinical professor in cardiology.

"Maybe a simple change of technique is what is necessary," he said. "The longer you hold the trigger, the higher the danger to the heart. ... The fewer pulses the better."

San Francisco, which does not use the devices, was not part of the study. Tseng declined to give specifics about local jurisdictions involved in the research but said that "Oakland did not give us data. San Jose did give us data."

Two years ago, Amnesty International reported 156 stun gun-related deaths of people in the United States during the previous five years.

The weapons have generated controversy, but a report last year which suggested a sweeping slate of reforms to the San Francisco Police Department said that allowing the use of Tasers may reduce injuries to officers and suspects.

Tasers are used by more than 12,000 law enforcement, military and correctional agencies in the U.S. and abroad, said UCSF's Lee.

More intensive research is needed, particularly within law enforcement agencies that show a high sudden death rate, said Samuel Walker, one of the nation's top police practices experts.

"We need good studies on the physiological impacts," said Walker, an emeritus professor of criminal justice at the University of Nebraska in Omaha. "I'd want to know more about the deaths, interview the officers to find out if they self-corrected."

The study's findings were published online this week by the American Journal of Cardiology.

Study tests REAL-WORLD effects of stun gun use

January 22, 2009
Digital Journal

University of California: San Francisco researchers have completed the first study to test real-world effects of stun gun use. Click here to read the abstract.

A University of California: San Francisco (UCSF) study states the rate of sudden deaths increased six-fold in the first year that California law enforcement agencies deployed the use of stun guns.

The findings also showed a two-fold increase in the rate of firearm-related deaths during the same time period.

The most widely used brand of stun gun is the Taser, and the team surveyed for outcomes related to the deployment of this device.

While some industry-funded controlled human studies have shown Tasers to cause no harm, this study suggests that their real-world effects pose greater medical risk and more danger than previous reports, said study author Zian H. Tseng, MD.

Although the device has been advertised to decrease the number of shooting deaths and officer injuries, study outcomes showed an increase rather than a reduction in the rate of shooting deaths and no change in officer injuries following Taser deployment, he added.

Researchers found that rates of sudden and firearm-related deaths declined back to near pre-deployment levels after the first year of Taser usage. The team postulated that law enforcement agencies self-corrected, likely adjusting their usage protocol or technique after the first year.

Study findings are published online today (Jan. 22, 2009) by the American Journal of Cardiology. The journal will also publish the study in an upcoming print edition.

“Physicians and law enforcement agencies need real-world knowledge of the effects of Taser use so that risks can be weighed in establishing appropriate policies and techniques,” said Tseng, who is senior author on the paper and assistant clinical professor in cardiology at UCSF.

“There have been a number of animal and controlled human studies, but none that test how Tasers are used in the real world, where subjects may have pre-existing medical conditions or be under the influence of narcotics.”

Researchers, under the Public Records Act and the Freedom of Information Act, mailed surveys to 126 police and sheriff departments in California cities and the 10 largest cities in the U.S. The survey requested three types of information: the rates of in-custody sudden deaths in the absence of lethal force, firearm-related deaths, and officer injuries requiring emergency room visits.

Fifty cities provided data on the rates of sudden death pre- and post-Taser deployment , while 21 cities reported firearm deaths and four cities reported officer injuries. None of the 10 largest U.S. cities returned surveys. The team used total annual arrest data per city as reported by the Department of Justice.

For each law enforcement agency that responded, researchers gathered data for the five years prior to the deployment of Tasers and for five years after. This allowed the research team, which included epidemiologists, cardiologists and statisticians, to observe how device deployment impacted the number of emergency events that a law enforcement agency experienced.

“Sudden deaths are extremely rare events, but it is important to look into why these events happen and whether law enforcement agencies are fully informed of the real-world risks of Taser deployment,” said Byron Lee, MD, first author on the paper and assistant clinical professor in cardiology at UCSF.

Stun guns like the Taser deliver a high-frequency, high-voltage current to incapacitate victims by causing momentary neuromuscular incapacitation. They are in use by over 12,000 law enforcement, military and correctional agencies in the U.S. and abroad, according to reporting by Taser International Inc.

Tasers were not examined in this study, but have been demonstrated to cause fatal ventricular tachyarrhythmias, or rapid irregular heartbeat, by capturing the heart at a higher, more dangerous rate. The increased adrenaline state resulting from a struggle and multiple, prolonged device applications near the heart may also make a person more vulnerable to sudden death.

“If law enforcement agencies using Tasers understood the risks and were trained to recognize cardiac arrest, sudden death events could be averted with timely deployment of external fibrillation or by knowing where not to apply the device’s current, such as near the heart,” Tseng said.

The research team noted limitations in its study, which was observational, such as a lack of information about reported sudden death events and the possibility that survey responses could be inaccurate. Also, the analysis only included a portion of cities known to be using the Taser. Several California cities and all of the largest U.S. cities surveyed were unwilling to release information.

“Further epidemiologic research is clearly needed. Without full transparency by law enforcement agencies, it is possible that our observed outcomes may actually be an underestimation of the real risks of Taser use,” Tseng added.

The study was funded by the National Center for Research Resources, a component of the National Institutes of Health and the NIH Roadmap for Medical Research.

Additional co-investigators on the study were Eric Vittinghoff, PhD, Dean Whiteman and Minna Park of UCSF; and Linda L. Lau of Loyola University Chicago School of Medicine.