New CDC report: Monkeypox testing in three patients resulted in false-positive findings

Federal health authorities on Friday warned in a report that a diagnostic test used to detect monkeypox in patients could result in “false-positive” test findings and may require retesting especially in suspected cases where the patient has low-risk factors of infection.

The report involved a healthy pregnant woman, an elementary school-aged previously healthy child and an infant.

All three patients were evaluated by health care providers after rashes and other symptoms appeared and “initially received positive Orthopoxvirus real-time PCR test results,” according to the Centers for Disease Control and Prevention (CDC). But after more testing, all patients tested negative for monkeypox, and clinicians ultimately diagnosed different conditions.

The CDC released its “Morbidity and Mortality Weekly Report” on Friday, showing that the Food and Drug Administration (FDA)-approved Orthopoxvirus real-time polymerase chain reaction (PCR) test triggered false positive results in three people who had characteristic symptoms, such as skin rashes and lesions.

The CDC noted in the report that patients with false-positive results could receive unnecessary treatments for the disease that has spread worldwide and across Florida. One of the patients did get treatment that would not have been necessary in connection with monkeypox.

Moreover, the CDC wrote in its report: “When testing specimens from patients with atypical signs and symptoms or without epidemiologic links or risk factors or where these are unknown, laboratories should reextract and retest specimens…to avoid unnecessary medical treatment and expenditure of public health resources.”

“Evaluation of these three patients for monkeypox highlights the need for caution in interpreting single laboratory test findings in patients with a low pretest probability of infection,” CDC wrote in the report.

Meanwhile, Florida’s monkeypox cases are closing in on 2,000, with the most infections in South Florida, according to data from the Florida Department of Health. Overall, there have been 1,991 cases across 36 counties, as of Friday afternoon. Miami-Dade County has seen 718 cases and Broward reported 597.