Comment: Serendipity and footwork each play a role in investigation

An investigation by the Maryland Department of Health and Mental Hygiene confirmed that an isotope contamination case was an isolated incident (see link below). What was extraordinary was the way local and state agencies put the pieces of the puzzle together.

Health officials in one Maryland county's communicable disease unit were notified on Nov. 12, 2004, about a case of acute hepatitis C. During an interview, the patient mentioned knowing someone similarly diagnosed at a different hospital. Their spouses worked together, and the two had met Oct. 15 at a clinic for a nuclear stress test, according to the DHMH report released on Monday.

An examination of clinic records revealed a third person whose hep C was reported to the county on Nov. 11. Coincidence was beginning to seem unlikely, according to the report. A further scrutiny of records showed that the three patients with confirmed hepatitis - and five others tested at the clinic on Oct. 15 - had been injected with doses of technetium-99m-labeled sestamibi prepared from the same pharmacy.

As the investigation focused on the pharmacy, the DHMH sent statewide alerts, requesting prompt entry of cases into the Maryland Electronic Reporting and Surveillance System. No other cases resulted from this effort. The DHMH and the Centers for Disease Control and Prevention began testing employees at the clinic and the pharmacy. These tests were negative.

Local and state officials expanded their investigation to other clinics that had received doses of the radionuclide drawn from the same lot number. In all, 16 cases in three different counties were found. An analysis of potential risk factors occurring at the time of incubation found individual cases of blood transfusion, renal dialysis, and surgery. But the only true commonality was that each had received a cardiac stress test on Oct. 15, 2004.

The pharmacy investigation revealed a number of procedural practices that could result in cross-contamination. A review of the records showed that the donor of labeled leukocytes, compounded on Oct. 15, had previously been diagnosed with hepatitis C. Genetic testing further revealed the donor's viral RNA to be genotype 1a, which matched 12 of 16 outbreak cases where the viral genotype could be determined.

Because of the time lag of a month between infection and initial outbreak, physical evidence at the pharmacy was minimal. Nonetheless, officials pieced together a convincing picture of the likelihood of the source of contamination.

The fact that the first patient interviewed by the DHMH could tell officials about a friend similarly diagnosed was a lucky stroke. After that, however, the investigation proceeded deliberately, with good coordination between the various governmental agencies, follow-up of leads, and analysis along the way of the available evidence.

For more information from the Diagnostic Imaging archives:

Contaminated radioisotopes cause hepatitis C infections