Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections (PANDAS) describes a medical condition where a Group A Streptococcus (GAS) infection triggers the sudden onset of severe neuropsychiatric symptoms in children. The immune response to the strep bacteria mistakenly attacks the brain, leading to inflammation and behavioral changes. Unlike many other infections, there is no single, definitive laboratory test to confirm a PANDAS diagnosis. Diagnosis relies on a detailed, multi-step process that combines clinical observation with specific laboratory evidence.
Understanding the Clinical Criteria
The process of testing for PANDAS begins with a thorough evaluation of the child’s symptoms and medical history. PANDAS is primarily a clinical diagnosis, requiring a physician to confirm five specific criteria established by the National Institute of Mental Health (NIMH). The first requirement is the presence of either an Obsessive-Compulsive Disorder (OCD) or a tic disorder, severe enough to interfere with the child’s normal function. These symptoms are often accompanied by other neuropsychiatric issues, such as separation anxiety, emotional lability, or difficulties with concentration.
A second criterion is pre-pubertal onset, meaning symptoms must first appear between the ages of three and the start of puberty. The third criterion is an unusually abrupt and dramatic onset of symptoms, or a relapsing-remitting course. Parents often recall the exact day their child’s behavior changed, with symptoms escalating rapidly over a matter of days.
The fourth criterion requires an association with a Group A Streptococcal infection, often confirmed through laboratory testing. The symptoms must be temporally related to the strep exposure, either at the initial onset or during subsequent symptom flares. Finally, the child must exhibit neurological abnormalities during symptom exacerbations. Common signs include motor hyperactivity, minor involuntary movements like choreiform movements, or a deterioration in fine motor skills, such as a change in handwriting.
The Role of Strep Antibody Testing
Once a child meets the clinical criteria, laboratory tests confirm the association with a recent Group A Strep infection. The most common tests are the anti-streptococcal antibody titers: the Anti-Streptolysin O (ASO) and the Anti-DNase B tests. These blood tests measure the level of antibodies the immune system produced in response to the strep bacteria. An elevated titer indicates recent exposure to a strep infection, which is required evidence for a PANDAS diagnosis.
These antibody tests do not diagnose PANDAS directly; they only confirm exposure to the bacteria. The ASO titer typically peaks three to six weeks after an acute infection, while the Anti-DNase B titer peaks slightly later, around six to eight weeks post-infection. Since titers from a prior infection can remain elevated for many months, a single high result does not definitively prove a recent infection caused the current symptoms.
Specialists may order a second set of titers six to eight weeks after the first to look for a four-fold rise, which is stronger evidence of a recent infection. A throat culture or rapid strep test is also often performed. However, a negative result does not rule out PANDAS, as the infection may have occurred weeks earlier or the bacteria may be present outside the throat. The combined use of these tests satisfies the requirement for a temporal relationship between strep exposure and the onset of neuropsychiatric symptoms.
Ruling Out Other Conditions
Because PANDAS is a diagnosis of exclusion, the diagnostic process must include testing to rule out other medical conditions that cause similar acute-onset neuropsychiatric symptoms. This differential diagnosis ensures the child’s symptoms are linked to the autoimmune response triggered by strep, not another underlying pathology. Conditions such as Sydenham chorea, a post-streptococcal autoimmune disorder, must be considered and excluded. Sydenham chorea presents with involuntary, jerky movements that can be mistaken for the neurological abnormalities seen in PANDAS.
Testing is also necessary to eliminate other potential infectious triggers, which would point toward a diagnosis of Pediatric Acute-onset Neuropsychiatric Syndrome (PANS). PANS is a broader category that includes PANDAS. Other infections, such as Lyme disease, Mycoplasma pneumonia, and certain viruses, can cause acute-onset symptoms, requiring specific blood tests. Furthermore, a physician will test for metabolic or endocrine disorders, such as thyroid dysfunction, which can also trigger psychiatric symptoms. This comprehensive screening ensures the final diagnosis is accurate and that any other treatable conditions are not overlooked.
Comprehensive Diagnostic Evaluation
The final stage of the PANDAS diagnostic process is the comprehensive evaluation, where a specialist synthesizes all gathered information. This process often involves a multi-disciplinary team, including pediatricians, neurologists, and child psychiatrists. The specialist reviews the child’s medical history, confirms that all five clinical criteria have been met, and assesses the significance of the strep antibody test results. Ultimately, the diagnosis is a clinical judgment based on the holistic picture, not the result of any single test.
The episodic course of the illness is a significant factor in this final review, requiring documentation of symptom timelines and previous test results. Parents are encouraged to bring symptom logs to the appointment, noting the severity and duration of each flare-up. The specialist weighs the clinical presentation, the timing of the neuropsychiatric symptoms relative to the strep infection, and the exclusion of other diagnoses to arrive at a final PANDAS diagnosis. This review ensures the child receives the most appropriate treatment plan based on medical evidence.