Introduction: Who Should Undergo Diagnostics and When

Parents should consider seeking diagnostic evaluation when their child experiences a sudden, dramatic change in behavior or mental health that seems to happen almost overnight. This is not the gradual development of symptoms that might occur over weeks or months, but rather an abrupt shift that can occur within just 72 hours or less.^[1] One week or even one day the child seems completely normal, and then suddenly they are unrecognizable to their family.

The most alarming signs that should prompt immediate medical attention include the sudden appearance of obsessive-compulsive symptoms—which are unwanted, repetitive thoughts or behaviors that the child feels compelled to perform—or a dramatic and severe restriction in eating where a child who ate normally suddenly refuses food or becomes extremely picky.^[2] These core symptoms typically appear alongside other troubling changes such as extreme anxiety, mood swings, tics (involuntary movements or sounds), difficulty sleeping, or changes in handwriting and motor skills.

It is especially important to seek evaluation if the child has recently had an infection, such as strep throat, a respiratory illness, or even flu-like symptoms. While not all children with PANS have a clear connection to infection, many cases appear to be triggered by the body’s immune response to bacteria or viruses.^[3] The connection between infection and sudden psychiatric symptoms is a key clue that helps distinguish PANS from other conditions.

Children between the ages of 3 and 12 are most commonly affected, though symptoms can appear up to puberty.^[4] Parents often describe feeling as though they have “lost” their child—the happy, social, well-adjusted child they knew has been replaced by someone who is terrified, aggressive, unable to function at school, or performing repetitive behaviors for hours on end. This sudden transformation is one of the most distinctive features of the condition and should not be dismissed as simply “going through a phase.”

Families should also be aware that these symptoms often follow a pattern of flares and periods of relative calm, known as a relapsing-remitting course.^[5] This means that symptoms may improve for a time and then suddenly return, sometimes triggered by another illness or stressor. Understanding this pattern can help parents recognize when to seek reevaluation and adjust treatment as needed.

Diagnostic Methods

Diagnosing PANS can be challenging because there is no single test that can confirm the condition. Instead, doctors rely on careful clinical evaluation based on specific criteria that describe the pattern and type of symptoms.^[6] The diagnosis is made when a child shows an unusually abrupt onset of obsessive-compulsive symptoms or severely restricted food intake, along with at least two other neuropsychiatric symptoms that also appear suddenly and severely.

The healthcare provider will begin with a thorough physical examination and detailed medical history. Parents will be asked to describe exactly when the symptoms started, how quickly they developed, and what the child was like before the symptoms appeared. This timeline is crucial because the sudden onset—typically within 72 hours—is a defining feature of PANS.^[7] The doctor will want to know about recent illnesses, infections, or other stressors that might have preceded the symptom onset.

To meet diagnostic criteria for PANS, the child must show sudden and severe onset of obsessive-compulsive disorder or eating restrictions, along with at least two of the following symptoms: anxiety (including separation anxiety), mood changes such as irritability or depression, behavioral regression (acting younger than their age), sudden decline in school performance, sensory sensitivities or motor problems including tics and changes in handwriting, sleep disturbances, or urinary symptoms such as frequent urination or bedwetting.^[8]

A subset of PANS is called PANDAS, which stands for Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections. PANDAS has its own specific diagnostic criteria that require evidence of a recent Group A streptococcal infection, such as strep throat or scarlet fever.^[9] To diagnose PANDAS, doctors will look for the presence of obsessive-compulsive disorder or tics, an age of onset between 3 years and puberty, acute onset and episodic course, association with strep infection, and the presence of neurological abnormalities.

Because strep bacteria can sometimes cause infection without typical symptoms like sore throat or fever, doctors may order throat cultures or blood tests to check for recent strep exposure even if the child did not seem obviously ill.^[10] These tests look for streptococcal antibodies in the blood, which indicate that the immune system has recently encountered the bacteria. A throat swab may also be taken to culture for active strep infection in the throat or other areas such as the perianal region.

An important part of the diagnostic process is ruling out other conditions that can cause similar symptoms. PANS is considered a diagnosis of exclusion, which means doctors must first eliminate other possible causes of the neuropsychiatric symptoms.^[11] Conditions that need to be considered and ruled out include Sydenham’s chorea (a movement disorder caused by rheumatic fever), autoimmune encephalitis (brain inflammation), systemic lupus erythematosus (an autoimmune disease that can affect the brain), and other neurological or medical disorders that might explain the symptoms.

Blood tests may be ordered to check for signs of inflammation or immune system abnormalities. These might include tests for markers of inflammation, autoantibodies, and evidence of recent viral or bacterial infections beyond strep.^[12] While no specific biomarker for PANS has been identified, these tests help build a picture of whether the immune system is reacting abnormally and help exclude other conditions.

In some cases, imaging studies such as MRI scans of the brain may be performed, particularly if there are concerns about other neurological conditions. Research has found that some children with PANS show abnormalities on brain scans, though these findings are not yet used as definitive diagnostic tools.^[13] These scans can, however, help rule out structural problems in the brain or signs of other diseases.

The evaluation should also include a detailed psychiatric assessment to document the specific obsessive-compulsive symptoms, anxiety, mood changes, and behavioral problems the child is experiencing. This helps establish the severity of symptoms and provides a baseline for measuring improvement with treatment. Many specialists use standardized rating scales to track symptom severity over time.^[14]

Because PANS is relatively rare and not all healthcare providers are familiar with it, families may need to seek out specialists with experience in the condition. Stanford Medicine established the first academic multidisciplinary PANS service in 2012, and similar specialized clinics have since been developed at other medical centers.^[15] These programs typically involve teams that include specialists in pediatric immunology, rheumatology, infectious disease, psychiatry, and neurology working together to evaluate and diagnose children with suspected PANS.

Diagnostics for Clinical Trial Qualification

For families interested in participating in research studies or clinical trials for PANS, there are additional diagnostic evaluations that may be required beyond standard clinical diagnosis. Clinical trials use specific criteria to ensure that participants truly have the condition being studied and to maintain consistency across research sites.^[16]

Most clinical trials for PANS require documentation that the child meets the established diagnostic criteria for PANS or PANDAS. This means having clear evidence of acute onset (within 72 hours or less) of obsessive-compulsive symptoms or eating restriction, along with at least two additional qualifying neuropsychiatric symptoms.^[17] Detailed medical records documenting the timeline of symptom onset and progression are typically required.

For trials specifically studying PANDAS, proof of a temporal association with streptococcal infection is necessary. This might include positive throat culture results, elevated streptococcal antibody titers in blood tests (such as anti-streptolysin O or anti-DNase B titers), or documented history of strep throat or scarlet fever occurring shortly before symptom onset.^[18] Some studies may have specific time windows—for example, requiring that strep infection occurred within a certain number of weeks before symptoms appeared.

Research protocols often include standardized psychiatric rating scales to measure the severity of obsessive-compulsive symptoms, anxiety, depression, and other psychiatric features. Common scales used in PANS research include the Children’s Yale-Brown Obsessive Compulsive Scale, which measures the severity of obsessions and compulsions, and various anxiety and mood rating instruments.^[19] Baseline scores on these scales may be required to fall within certain ranges to qualify for study participation.

Some clinical trials may require specific laboratory testing to characterize the immune response or inflammatory state. This could include more detailed immunological testing than is done for routine clinical diagnosis, such as comprehensive autoantibody panels, cytokine measurements, or specialized tests looking at immune cell function.^[20] These tests help researchers understand the underlying mechanisms of the disease and whether particular immune abnormalities predict treatment response.

Exclusion criteria are also important in clinical trials. Research studies typically exclude children who have other conditions that might confound the results, such as other autoimmune diseases, neurological disorders, or psychiatric conditions that developed gradually rather than acutely. Complete medical records documenting that other conditions have been ruled out may be required.^[21]

Age requirements vary by study, but most PANS clinical trials focus on children within the typical age range for the condition—usually between 3 years and the onset of puberty or up to age 18. Some studies may have more specific age restrictions or may be designed for particular subgroups, such as only children with recent-onset symptoms versus those with chronic, long-standing illness.^[22]

Neuropsychological testing may be included in some research protocols to document cognitive function, attention, memory, and executive function—the mental skills that help with planning and organization. This testing provides objective measures of how PANS affects brain function and can help track whether treatments improve not just psychiatric symptoms but also cognitive abilities.^[23]

For families considering clinical trial participation, it is important to understand that research studies may require more frequent visits and more extensive testing than routine clinical care. This might include regular blood draws to monitor immune markers, repeated rating scale assessments, imaging studies, or other procedures depending on the study design. Families should discuss the specific requirements and time commitment with the research team before enrolling.^[24]