Strategies to cope with PPD shortage
Hospitals delay screening, switch to IGRAs
A shortage of a major TB skin-testing product forced some hospitals to alter their health care worker screening programs, but it also demonstrated the ability of employee health departments to adapt to change circumstances.
Due to manufacturing problems, Tubersol, a purified protein derivative (PPD) tuberculin product of Sanofi Pasteur, was in short supply in March, and was available only in 10-test vials in May. Supply of the 50-test vials was expected to resume in late May.
Some facilities switched to Aplisol, a PPD manufactured by JHP Pharmaceuticals, leading to spot shortages of that product.
“It shows the fragility of the pipeline for key products like this,” says T. Warner Hudson, MD FACOEM, FAAFP, medical director of Occupational and Employee Health at the UCLA Health System and Campus.
Hudson never had an interruption in supply of PPD, but he immediately created a backup plan that involved doing more blood testing. UCLA already is gradually transitioning to QuantiFERON-TB Gold by using it with new hires.
“It’s a lucky coincidence that QuantiFERON and T-Spot [another interferon-gamma release assay or IGRA blood test] are emerging as possible replacements,” he says.
Some hospitals responded to the shortage by delaying routine health care worker screening and using the available supply for patients and exposure situations.
“It took us less than a day to get an action plan in place,” says Lynn Vining, RN, MSN, CPHQ, nurse manager in the Employee Health Clinic at the University of Iowa Hospitals and Clinics in Iowa City. “We had all bases covered if we needed to. That plan was written with all the case scenarios that could possibly happen.”
The Centers for Disease Control and Prevention suggested three alternatives to cope with the shortage, but left it up to facilities to decide how to proceed:
• Substitute IGRA blood tests for skin-testing.
• Defer some testing and use the available supply for priority testing.
• Substitute Aplisol for Tubersol — if it’s available.
Switching between skin-testing and blood-testing can be problematic, notes John Jereb, MD, medical officer with CDC’s Division of TB Elimination.
“If you have a hospital with a program where the employees have been tested every year or two years [and] you switch from the skin test to IGRAs, you’re going to get different results for a few employees and that will be confusing,” he says.
It would be hard to determine whether the unexpected result was due to latent TB infection or a false positive result from a different test, he says.
The PPD shortage may cause some facilities to take a closer look at IGRAs and to learn more about the differences between the tests, he says.
“One of the silver linings is that in the specialty of TB control and the public health community, we have been forced to reexamine the role of skin testing in TB diagnosis, in screening, and in infection control,” Jereb says. “That can only be healthy.”
Meanwhile, as the Tubersol shortage was subsiding, CDC reported a “severe interruption” in the supply of isoniazid, a first-line drug for the treatment of latent TB infection.
The shortages reflect a public health concern, says Hudson. “There are products that are public health necessities that need to be protected, subsidized, and supported,” he says.
1. Centers for Disease Control and Prevention. National shortage of purified-protein derivative tuberculin products. MMWR 2013;62:312.