A blood test aids the diagnosis of cervical lymphadenitis in children

A blood test-based method of diagnosing NTM cervical lymphadenitis in children has been known for years, but its reliability has now been confirmed using real-world patient data. For the first time, the study also determined the cut-off values for a PPD response–that is, a positive test result–based on actual patient cases.

The research findings make it possible to move away from invasive research methods and antibiotics 

The first findings regarding the suitability of this blood test for diagnosing NTM lymphadenitis in children were published ten years ago. Despite this, invasive procedures such as biopsies and surgical interventions are still frequently used in diagnosis and treatment.

“The fact that our study was able to confirm the reliability of the blood test for diagnostic purposes will hopefully pave the way for a move away from invasive procedures. Taking a biopsy from a child requires anesthesia, and the surgical procedure leaves a scar," says Anne Toivonen, a specialist in clinical microbiology.

In addition to the continued use of invasive diagnostic methods, lymphadenitis is often treated with antibiotics before the diagnosis is confirmed. NTM cervical lymphadenitis in children resolves on its own, and treatment usually only involves monitoring. Once the cause of the infection has been confirmed by a blood test, there is no need for antibiotics.

In Finland, NTM cervical lymphadenitis is rare in children. A symptom of lymphadenitis is a lump that appears on the neck within a short period of time.

The blood test can also be used to determine a child's vaccination status

The BCG vaccine produces a positive result in the blood test used to diagnose NTM lymphadenitis. This means that blood test-based diagnostic methods can be used in non-BCG-vaccinated children. In Finland, the BCG vaccine has been given only to high-risk groups since 2006. 

“In ambiguous cases, our findings also make it possible to use the same blood test to determine whether a child has been vaccinated,” Toivonen says. 

The study data consisted of test results and clinical data from 939 pediatric patients, all of whom had been tested at HUS between 2011 and 2015. The data set identified 45 children with NTM cervical lymphadenitis. Of these cases, 15 were confirmed by culture, and the remaining 30 were diagnosed based on clinical evaluation, histology, and an elevated PPD response. All 45 children with a diagnosis were included in the study group for the purpose of calculating the PPD cut-off value. The control group consisted of 141 healthy, non-BCG-vaccinated children with recent contact with a mycobacterium tuberculosis-positive case. As these children had not been diagnosed with tuberculosis—the condition for which the blood test under review was originally developed—they comprised a suitable control group for normal PPD values.

The study was published in the Journal of Pathology, Microbiology and Immunology.

Research article: The Use of Purified Protein Derivative (PPD) Response in Elispot IGRA for the Diagnosis of Nontuberculous Mycobacterial Cervical Lymphadenitis

In university hospitals research is part of treatment: new research outcomes make treatment practises more efficient and help focus treatments correctly. We work in close collaboration with the University of Helsinki and other universities, and we publish ca 3,000 peer-reviewed research articles annually.

Today’s research provides better care in the future.

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