Additional Tests after Spinal Tap May Be Excessive

A new study from neurology, infectious disease and ophthalmology researchers at Children’s Hospital of Philadelphia (CHOP) found that non-culture cerebrospinal fluid (CSF) infection tests were frequently ordered on children with healthy immune systems who underwent lumbar puncture (or spinal tap), even when they had normal CSF white and red blood cell counts. In addition, positive results in these children were rare and unlikely to be independently associated with their clinical care. The findings were published in the journal JAMA Network Open on July 19, 2019.

The researchers concluded that delaying the decision to send non-culture CSF infection tests until CSF cell counts are available could reduce unnecessary diagnostic testing and medical costs, which may improve value-based care.

Jennifer McGuire, MD Jennifer McGuire, MD, a pediatric neurologist in the Division of Neurology at CHOP, and her colleagues studied the records of more than 4,000 children with healthy immune systems. The children in the study were between 6 months and 18 years of age and underwent a spinal tap at CHOP. Most of these children (69%) had normal cell counts.

When a child has meningitis or encephalitis, their CSF white blood cell count is typically elevated because these are the cells that fight infection; a normal CSF white blood cell count is generally reassuring. Despite this, 1,270 of these children with normal cell counts still received at least one non-culture CSF infection test, such as polymerase chain reaction and antigen or antibody assays, each of which are used to identify specific pathogens in suspected central nervous system infections. The researchers suggested this may happen because clinicians do not always wait to see CSF cell count results before ordering additional testing.

The study team found that only 18 of those 1,270 lumbar puncture specimens with normal cell counts had a positive non-culture infection test. Of those 18 children, only two required clinical intervention, but each of those patients also had other clear clinical signs of infection.

“This current study demonstrates that the yield of sending non-culture CSF infection testing on spinal fluid from children with healthy immune systems and normal CSF cell counts is very low,” McGuire said. “Rather than order these tests across the board, we hope these data help clinicians take a more nuanced approach to testing. Delaying the decision to send these tests until CSF cell counts are available, unless they have a specific, active clinical concern for an infection, could dramatically improve value-based care.”

Read the abstract: "Assessment of Diagnostic Yield of Nonculture Infection Testing on Cerebrospinal Fluid in Immune-Competent Children."