A survey of about 430 clinical-trial sites in the U.S. found that the workload associated with creating consent forms and pursuing reimbursement from the trial sponsors is the main reason many of them do not offer transportation services to patients.

According to the survey, which was conducted by Continuum Clinical in February, only 44% of these sites offer free transportation assistance to people who are enrolled in their clinical trials. And of the sites that do offer transportation, 58% of them rely on taxi services, while 32% of them use ride-sharing companies such as Lyft and Uber. In January, Continuum announced a partnership with Lyft to offer free rides to patients enrolled in clinical trials organized by its clients, and interest is growing in using the ride-sharing services.

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But there are underlying challenges with providing transportation to participants enrolled in clinical trials, said Nariman Nasser, vice president of site optimization at Continuum Clinical.

“Where the transportation service comes in is there needs to be consent for the patient to utilize the transportation option,” said Nasser.

Instead of having to go through patient consent forms that are often as long as 20 pages, the patient only needs to re-consent for the patient transportation portion of the clinical trial when participating in a trial organized by one of Continuum’s sites, explained Nasser.

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Securing transportation for patients is an issue for the healthcare industry in general, and that is why ridesharing companies are increasingly getting involved in the healthcare market, in part by partnering with hospitals and insurers to address high rates of missed or delayed doctor’s visits, according to the Blue Cross Blue Shield Association. In May, the health insurer announced a partnership with Lyft to provide free transportation to certain members. Last September, Lyft’s competitor Uber also began providing patients with non-emergency transportation to a number of hospitals through a partnership with technology startup Circulation.

“Of the sites that are providing patient transportation, mostly in the form of taxi, that’s only provided to elderly and low-income patients,” Nasser said. “It makes sense that they’re providing transportation to those with the most obvious needs, but we know from our data, particularly in the U.S., the majority of clinical trial patients tend to be middle-aged, give-or-take, middle-class individuals.”