Which test is primarily used to confirm a diagnosis of meningitis in a child?

The lumbar puncture is the primary test used to confirm a diagnosis of meningitis in a child because it allows for direct analysis of the cerebrospinal fluid (CSF). During a lumbar puncture, a needle is inserted into the spinal canal to collect CSF, which can then be examined for the presence of pathogens, such as bacteria or viruses, as well as for signs of inflammatory responses. This analysis can reveal abnormal white blood cell counts, elevated protein levels, and decreased glucose levels, which are characteristic findings in meningitis.

In contrast, a CT scan may be employed to assess for complications or to rule out other conditions, such as structural abnormalities or intracranial pressure, but it does not provide definitive information about the presence of meningitis. An X-ray is not useful for diagnosing meningitis, as it does not visualize the central nervous system or provide relevant information about CSF composition. Blood cultures can help detect systemic infections that might cause meningitis but are not specific or definitive for diagnosing this condition. Thus, the lumbar puncture is essential for confirming meningitis and guiding appropriate treatment.