Published: Nov 27, 2013
By Michael Smith, North American Correspondent, MedPage Today
Screening for HIV among people entering a prison system might not pick up a lot of new cases, researchers reported.
In an 11-month period, HIV testing of new inmates in North Carolina found that 1.45% of them had HIV, according to David Wohl, MD, and colleagues at the University of North Carolina in Chapel Hill, N.C.
But only a handful of those cases -- less than 0.1% -- were previously undiagnosed, Wohl and colleagues reported in the Nov. 27 issue of the Journal of the American Medical Association.
The finding suggests that undiagnosed HIV might be relatively rare among prisoners, contrary to the common perception that prisons are hotbeds of unknown infections, Wohl argued.
"The whole concept is let's screen these people because we'll find undetected, undiagnosed HIV; that there's going to be a wellspring of undetected HIV," he told MedPage Today. "We found that was not the case at all in our state."
In North Carolina, an HIV test on prison entry was voluntary during the study period in 2008-2009, but a syphilis test was mandatory, Wohl and colleagues noted.
HIV testing is now mandatory in the state's prisons, Wohl said.
The researchers used excess blood from the syphilis tests for an HIV assay, but before the HIV results were de-identified, they were compared with the North Carolina Department of Health and Human Services HIV testing database.
Of the 23,373 people who entered the system from June 2008 through April 2009, 22,134 (94.7%) had sufficient excess blood to allow HIV testing.
All told, 320 inmates (1.45%) were HIV-positive, but 300 were already known to be infected with HIV.
In other words, just 20 of 22,134 new inmates were HIV-positive -- 0.09% -- and not previously known to be, Wohl and colleagues found.
Among the 1,239 new inmates without enough excess blood for HIV testing, 1,066 had a voluntary test in prison and 36 (4.8%) were HIV-positive. All 36 were previously known by the state health department to be infected, Wohl and colleagues reported.
"I was astounded that 94% of people coming into prison who have HIV were already known to have HIV," Wohl said.
The study suggests that aggressive testing in prisons is unlikely to reap a good yield of new HIV cases, Wohl said.
"If you want to go find a place where there's a lot of people undiagnosed with HIV, the prison population in North Carolina is not it," he said.
The prevalence of HIV among the new inmates -- about 1.43% among all of those who were tested -- is about the same as the CDC estimate of 1.4% among the national prison population, both state and federal.
Other researchers have found relatively high rates of HIV among people held in local jails, usually for short periods of time, before they are released or sent on to prison.
But it's "likely that the prison population is fairly representative of what we're talking about in jails," Wohl said, although the jail population is larger.
Wohl and colleagues cautioned that it's possible that a known HIV diagnosis might have resulted from screening during a previous prison term, although almost half the people with a known infection had not previously been incarcerated.
They also noted that North Carolina has the eighth highest HIV prevalence in the U.S. and the findings of the study might not apply to other states.
The study had support from the National Institute of Mental Health and the University of North Carolina Center for AIDS Research.
Wohl reported financial links with Janssen, Gilead, GlaxoSmithKline, and ViiV.
Primary source: Journal of the American Medical Asssociation
Source reference: Wohl DA, et al "Detection of undiagnosed HIV among state prison entrants"JAMA 2013; 310(20): 2198-2199.