Overview
System Interactions holds 8 to 10 of the 180 scored NPTE-PT items, about 4 to 6 percent. In the 2024 FSBPT outline it has only a foundations for evaluation, differential diagnosis and prognosis category, with no separate examination or interventions categories. FSBPT lists seven content statements, and this guide uses each one as a topic.
The statements cover conditions that affect more than one system, such as cancer, multitrauma, sarcoidosis, autoimmune disorders and pregnancy; medical tests and surgery across systems; drugs used for several systems, including polypharmacy; differential diagnosis of multisystem conditions; comorbidities like diabetes with hypertension, obesity with arthritis and dementia with hip fracture; psychological and psychiatric conditions such as grief, depression and schizophrenia; and the psychological, social, physiological, neurological and mechanical dimensions of acute or persistent pain.
How it's tested
System Interactions items are usually longer vignettes with several conditions, a medication list, labs or psychosocial details. The question asks which factor most changes the plan, what is the most likely explanation for a new finding, or how to modify care. Sort the details by system and look for the one that creates a safety issue or a referral.
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The decisive comorbidity
Several diagnoses are listed, and you choose the one that most alters exercise safety, prognosis or the order of priorities.
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Drug interaction effects
A medication list in an older adult is given, and you identify the likely cause of dizziness, falls or confusion.
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Biopsychosocial pain
Persistent pain with fear, catastrophizing or social stress is described, and you pick education or graded activity over passive care.
A patient with persistent low back pain for two years avoids bending, scores high on a fear-avoidance questionnaire, and imaging shows age-typical disc changes. Choosing another passive modality treats the pain as purely mechanical. The better answer is pain neuroscience education with graded exposure to feared movements, because the fear and avoidance are now sustaining disability.
Content areas 7
Official content areas from the FSBPT outline, in outline order.
6.1 Diseases/conditions that primarily affect more than one system (e.g., cancer, multitrauma, sarcoidosis, autoimmune disorders, pregnancy) and their impact on the plan of care and prognosisMultisystem conditions and how they shape plans and outcomes.
- What it means
- This statement covers conditions whose effects spread across several body systems, so the physical therapist must plan care around cardiovascular, musculoskeletal, neurologic and other effects at the same time.
- What to understand
- For cancer, know red flags, effects of chemotherapy and radiation (fatigue, neuropathy, cardiotoxicity, low blood counts) and bone metastasis fracture risk. For pregnancy, know physiologic changes such as ligament laxity and increased blood volume, avoiding prolonged supine positions after the first trimester, warning signs to stop exercise, and diastasis recti. For multitrauma, prioritize life-threatening injuries and weight-bearing orders. For autoimmune diseases such as lupus and sarcoidosis, know flare management and organ involvement.
- How it shows up
- Expect a multisystem patient and a question about the safest plan, a needed modification or the expected prognosis.
- Common confusion
- Using standard intensity for a patient whose blood counts are low from chemotherapy.
6.2 Nonpharmacological medical management of multiple systems (e.g., diagnostic imaging, other medical tests, surgical procedures)Tests, imaging and surgery that cut across systems.
- What it means
- This statement covers how medical tests and procedures that involve several systems shape physical therapy decisions, including lab panels, imaging findings and surgeries with wide physiologic effects.
- What to understand
- Know common lab values and what each means for activity: hemoglobin, platelets, white cell count, INR, electrolytes and glucose. Understand what imaging reports mean for loading and when imaging is not needed. Know the multisystem effects of major surgery, such as anesthesia, immobility, blood loss, DVT risk and post-operative delirium, and of procedures like bariatric surgery, stem cell transplant and organ transplant, including immunosuppression and infection precautions.
- How it shows up
- Items present lab or imaging results and ask whether therapy should continue, be modified or be held.
- Common confusion
- Ignoring a critical lab value because the patient reports feeling well.
6.3 Impact of pharmacology used to treat multiple systems, including polypharmacy, on physical therapy managementDrug effects and interactions across systems.
- What it means
- This statement covers medications whose effects reach several systems and the added risk when patients, often older adults, take many drugs at once.
- What to understand
- Know how sedatives, opioids, antihypertensives, diuretics, anticholinergics and antidepressants contribute to dizziness, orthostatic hypotension, confusion and falls. Recognize corticosteroid effects on bone, muscle, skin and glucose; anticoagulant bleeding risk; and statin-related muscle pain. Know that polypharmacy is commonly defined as five or more medications and that lists such as the Beers Criteria flag drugs that are risky in older adults. The physical therapist reports suspected adverse drug effects to the prescriber rather than changing medications.
- How it shows up
- Expect a patient with falls or new confusion and a question about the most likely contributor or the right action.
- Common confusion
- Advising a patient to stop a medication instead of communicating with the prescriber.
6.4 Differential diagnoses related to diseases/conditions that primarily affect more than one systemSeparating multisystem disease from single-system problems.
- What it means
- This statement covers recognizing when signs across several systems point to one underlying condition, or when a complaint that looks local is part of a systemic disease that needs medical care.
- What to understand
- Look for constitutional signs such as fever, night sweats, unexplained weight loss and fatigue, and for patterns across systems: joint pain with rash and kidney findings in lupus, lung and skin signs in sarcoidosis, or back pain with weight loss and a cancer history. Know when findings warrant referral and how to prioritize urgent problems. Screening tools for medical referral help organize this reasoning, and the physical therapist's role is to recognize and refer, not to confirm a medical diagnosis.
- How it shows up
- Questions ask which finding is most concerning or what the next step should be when symptoms span systems.
- Common confusion
- Explaining away systemic signs because the main complaint is musculoskeletal.
6.5 Impact of comorbidities/coexisting conditions on patient management (e.g., diabetes and hypertension, obesity and arthritis, dementia and hip fracture)How coexisting conditions change the plan.
- What it means
- This statement covers adjusting examination, goals and interventions when a patient has more than one condition, because each one limits or reshapes care for the others.
- What to understand
- With diabetes and hypertension, monitor glucose and blood pressure and watch for silent ischemia and neuropathy. With obesity and knee osteoarthritis, use lower-impact aerobic options, weight management support and joint-friendly strengthening. With dementia after hip fracture, use simple cues, routines and caregiver training, and expect slower progress and higher delirium risk. Prognosis worsens as comorbidity burden rises, so goals and discharge plans must reflect it.
- How it shows up
- Expect items that ask which modification best fits a patient with two or more listed conditions.
- Common confusion
- Planning for the primary diagnosis only and ignoring the coexisting condition.
6.6 Psychological and psychiatric conditions that impact patient management (e.g., grief, depression, schizophrenia)Mental health factors that shape care.
- What it means
- This statement covers how mood, grief, anxiety, psychotic disorders and similar conditions affect engagement, safety and outcomes, and when the physical therapist should screen and refer.
- What to understand
- Know brief screens such as the PHQ-2 and PHQ-9 for depression and when to refer. Any statement of suicidal thoughts requires immediate action and referral following facility policy. Understand how depression lowers motivation and adherence, how grief may follow amputation or loss of function, and how antipsychotic drugs can cause movement disorders such as tardive dyskinesia and orthostatic hypotension. Communication should be clear and respectful, with consistent routines.
- How it shows up
- Items ask for the best response to a psychological concern raised during therapy, or how a psychiatric condition changes the approach.
- Common confusion
- Continuing routine treatment after a patient discloses suicidal thoughts.
6.7 Dimensions of acute or persistent pain that impact patient management (e.g., psychological, social, physiological, neurological, mechanical)Pain as a multidimensional experience.
- What it means
- This statement covers understanding pain through a biopsychosocial model, recognizing nociceptive, neuropathic and nociplastic pain, and adjusting care to the factors that drive each person's pain.
- What to understand
- Acute pain usually tracks tissue injury and improves with healing. Persistent pain often involves central sensitization, fear-avoidance, catastrophizing, poor sleep and social stress. Know screening tools such as the Fear-Avoidance Beliefs Questionnaire, Pain Catastrophizing Scale and STarT Back Tool. Interventions include pain neuroscience education, graded activity, graded exposure and active, function-focused goals rather than reliance on passive care. Neuropathic pain features burning, shooting pain and allodynia.
- How it shows up
- Expect cases where psychosocial factors drive disability and the best answer addresses beliefs and behavior.
- Common confusion
- Assuming pain intensity always reflects the amount of tissue damage.
High-yield concepts
The terms, rules and formulas this domain turns into questions most often.
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Platelet thresholds
Platelet count guides exercise safety.
- Remember
- Below about 20,000 limits activity to light ADLs; resistance waits until counts rise.
- Tested as
- Oncology and hematology cases.
- Trap
- Prescribing resistance with very low counts.
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Neutropenia precautions
Low white cells increase infection risk.
- Remember
- Use masks, hand hygiene and avoid crowded gyms.
- Tested as
- Oncology cases.
- Trap
- Ignoring infection control.
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Bone metastasis
Cancer spread to bone.
- Remember
- Higher fracture risk; avoid heavy loading and torsion.
- Tested as
- Exercise selection.
- Trap
- Treating new back pain in a cancer history as mechanical.
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Pregnancy exercise
Physiologic changes in pregnancy.
- Remember
- Avoid prolonged supine after the first trimester; stop for bleeding or contractions.
- Tested as
- Women's health cases.
- Trap
- Prescribing supine core work late in pregnancy.
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Polypharmacy
Use of many medications, often five or more.
- Remember
- Raises risk of falls and adverse effects.
- Tested as
- Older adult cases.
- Trap
- Telling the patient to stop a drug.
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Orthostatic hypotension
BP drop on standing.
- Remember
- Systolic fall of 20 mmHg or diastolic 10 mmHg within 3 minutes.
- Tested as
- Fall risk and drug effects.
- Trap
- Missing it after medication change.
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Constitutional symptoms
Fever, night sweats, weight loss, fatigue.
- Remember
- Suggest systemic disease and need referral.
- Tested as
- Screening items.
- Trap
- Treating them as stress.
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Delirium
Acute, fluctuating confusion.
- Remember
- Often triggered by surgery, infection or drugs in older adults.
- Tested as
- Post-op and dementia cases.
- Trap
- Calling new confusion dementia.
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PHQ-2
Two-item depression screen.
- Remember
- Positive screen leads to fuller assessment and referral.
- Tested as
- Psychological factors.
- Trap
- Diagnosing depression from it.
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Suicide risk response
Action when a patient reports suicidal thoughts.
- Remember
- Stay with the patient and follow the referral policy immediately.
- Tested as
- Safety and ethics.
- Trap
- Waiting until the next visit.
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Central sensitization
Amplified nervous system response to input.
- Remember
- Widespread pain and hypersensitivity out of proportion to tissue findings.
- Tested as
- Persistent pain cases.
- Trap
- Searching for a single tissue source.
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Fear-avoidance
Avoiding movement due to fear of pain or harm.
- Remember
- Use graded exposure and education.
- Tested as
- Persistent pain cases.
- Trap
- Recommending rest.
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Pain neuroscience education
Teaching how pain works.
- Remember
- Reduces threat and supports active recovery.
- Tested as
- Persistent pain interventions.
- Trap
- Using it as the only treatment.
Side by side
Concepts candidates mix up, compared on the point that decides the answer.
Types of pain
| Concept | Meaning | Key difference | Common trap |
|---|---|---|---|
| Nociceptive | Pain from tissue injury or inflammation | Localized, related to load and movement | Treating it with neuropathic strategies |
| Neuropathic | Pain from nerve damage or disease | Burning, shooting, numbness, allodynia | Calling it muscular |
| Nociplastic | Pain from altered nociceptive processing | Widespread, poorly localized, sensitized | Searching for a tissue lesion |
Delirium versus dementia
| Concept | Meaning | Key difference | Common trap |
|---|---|---|---|
| Delirium | Acute brain dysfunction | Sudden onset, fluctuating attention, often reversible | Treating it as baseline |
| Dementia | Chronic progressive cognitive decline | Gradual onset, stable attention early | Expecting rapid change |
Acute versus persistent pain
| Concept | Meaning | Key difference | Common trap |
|---|---|---|---|
| Acute pain | Recent onset tied to tissue injury | Protective; expected to resolve with healing | Over-applying psychosocial labels |
| Persistent pain | Lasting beyond expected healing, often over 3 months | Shaped by sensitization and psychosocial factors | Relying on passive modalities alone |
Exam traps
Each trap is an answer that looks right. Learn the clue that should change your mind.
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Resistance with low counts
- What candidates pick
- Prescribe progressive resistance for cancer-related fatigue.
- Why it looks right
- Exercise helps cancer-related fatigue.
- Why it's wrong
- Very low platelets raise bleeding risk; light activity is appropriate until counts recover.
Clue to watch for Platelet value in the stem.
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New confusion is dementia
- What candidates pick
- Assume the patient's dementia is progressing.
- Why it looks right
- The patient has a dementia history.
- Why it's wrong
- Sudden, fluctuating confusion suggests delirium from infection, drugs or surgery and needs medical review.
Clue to watch for Rapid change over hours or days.
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Adjusting medications
- What candidates pick
- Advise the patient to skip a blood pressure pill before therapy.
- Why it looks right
- It appears to solve the dizziness.
- Why it's wrong
- Medication changes belong to the prescriber; the PT reports findings and adapts the session.
Clue to watch for Medication timing linked to symptoms.
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Find the pain generator
- What candidates pick
- Choose more imaging or a new passive modality for chronic pain.
- Why it looks right
- A precise tissue target feels scientific.
- Why it's wrong
- In persistent pain, fear, sensitization and beliefs often drive disability more than tissue findings.
Clue to watch for High fear-avoidance or catastrophizing scores.
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Supine exercise in late pregnancy
- What candidates pick
- Include supine abdominal work in the third trimester.
- Why it looks right
- Core strength helps pregnancy.
- Why it's wrong
- Prolonged supine positions after the first trimester can compress the vena cava and lower cardiac output.
Clue to watch for Pregnancy beyond the first trimester.
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Ignoring weight loss
- What candidates pick
- Continue spinal treatment for back pain with unexplained weight loss.
- Why it looks right
- The pain behaves mechanically.
- Why it's wrong
- Unexplained weight loss with a cancer history is a red flag that needs medical referral.
Clue to watch for History of cancer plus constitutional symptoms.
Answer framework
Use this approach for multisystem and persistent pain scenarios.
- List every condition, medication, lab value and psychosocial factor in the stem and note which system each affects.
- Identify any immediate safety issue, such as a critical lab value, signs of delirium, suicidal statements or red flags for serious disease.
- Decide which factor most limits the plan or prognosis, rather than focusing only on the referring diagnosis.
- Choose a modification or referral that addresses that factor, such as adjusting intensity, coordinating with the prescriber or screening for depression.
- For pain, classify the dominant pain type and drivers, then favor education, graded activity and active goals over purely passive care, and recheck function and beliefs with a standardized tool over time.
Practice question
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Study strategy
This area depends on knowledge from every other domain, so study it after a first pass through the body systems. Start with a lab value sheet that lists the value, its normal range and the activity decision it drives. Then add an oncology page covering treatment side effects, blood count precautions, bone metastasis and lymphedema risk, and a pregnancy page with physiologic changes and stop signs.
Next, review pharmacology across systems. Group drugs by the side effects that matter to therapy: dizziness, orthostatic hypotension, sedation, bleeding, muscle pain, glucose change and bone loss. Practice explaining what you would report and to whom.
Finish with psychosocial content and pain science. Learn the screening tools, the referral pathways for depression and suicide risk, and the features of nociceptive, neuropathic and nociplastic pain. Work through long mixed cases and, for each, write down which detail changed the answer before checking the written explanation.
FAQ
How much of the NPTE-PT is System Interactions?
System Interactions has 8 to 10 of the 180 scored items, about 4 to 6 percent, all in the foundations for evaluation, differential diagnosis and prognosis category.
Why does System Interactions have no interventions category?
FSBPT tests interventions within each body system and nonsystem area. System Interactions focuses on evaluation, differential diagnosis and prognosis when several systems are involved.
Is oncology tested here?
Yes. Cancer is named as an example of a condition that affects more than one system, so expect treatment side effects, lab precautions and red flags.
How much pain science is on the exam?
The 2024 outline names psychological, social, physiological, neurological and mechanical dimensions of acute or persistent pain, so expect biopsychosocial reasoning rather than tissue-only explanations.
What should I do if a patient mentions suicidal thoughts?
Take it seriously, keep the patient safe, and follow facility policy for immediate referral. Do not continue routine care as if nothing was said.
Which comorbidity combinations should I practice?
The outline gives diabetes with hypertension, obesity with arthritis and dementia with hip fracture as examples. Practice adapting goals and dosing for each pair.
Test your Domain 6 knowledge
You have reviewed multisystem conditions, drug effects, psychosocial factors and pain. Test whether you can find the deciding detail in long, mixed vignettes.
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