Facts read from aanpcert.org and 2 more · last checked Nov 7, 2026
Diagnose items hand you the history, the examination and often a lab value, then ask for the most likely diagnosis or the one you cannot afford to miss. This task is 26.5% of the scored exam, 36 of 135 items.
Practice questions
60 questions written to the FNP-C outline; each choice is explained once you pick.
Synthesize: put subjective and objective data together into a list of possible diagnoses.
Prioritize: rank that list and settle on the primary diagnosis, keeping the dangerous alternatives in view.
Typical stems: “Which diagnosis is most likely”, “These findings are most consistent with”, “Which condition must be excluded first”.
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15 Diagnose questions
0 / 15 answered15 questions
Tap an option: why each one is right or wrong appears under it.
Diagnose · 26.5%
A 22-year-old preschool teacher has 2 weeks of symmetric pain and swelling of the MCP and PIP joints, wrists, and knees with morning stiffness and low-grade fever. Several children in her class recently had bright red cheeks followed by a lacy rash. Which test is most likely to confirm the diagnosis?
Uric acid relates to gout, which is usually a monoarthritis of the big toe, ankle, or knee; levels are also unreliable during a flare.
HLA-B27 is linked to spondyloarthritis, which causes back pain and asymmetric large-joint arthritis, not symmetric small-joint disease after viral exposure.
Symmetric small-joint arthritis in an adult exposed to children with 'slapped cheeks' and a lacy rash is parvovirus B19 arthritis, confirmed by B19 IgM; it usually resolves within weeks to months.
Anti-CCP supports rheumatoid arthritis, which needs 6 weeks or more of symptoms to classify; a 2-week course after exposure to erythema infectiosum points elsewhere, and RF can be transiently positive in parvovirus.
A 52-year-old woman has 1 year of gritty eyes and a dry mouth that makes her sip water to swallow bread. She has had three new dental caries this year and recurrent bilateral parotid swelling. She takes no anticholinergic or antihistamine drugs. Chest radiograph is normal. What is the most likely diagnosis?
Lupus can cause sicca too, but it presents with rash, cytopenias, serositis, or kidney disease.
Sarcoidosis can enlarge the parotid glands, but it usually shows hilar lymphadenopathy, and her chest radiograph is normal.
Rheumatoid arthritis can cause secondary Sjögren syndrome, but it presents first with symmetric inflammatory arthritis, which she does not have.
A year of dry eyes and mouth with new caries and recurrent parotid swelling, without drying drugs, fits primary Sjögren syndrome; anti-SSA (Ro) and anti-SSB (La) antibodies support it.
A 26-year-old woman of East Asian descent has 1 year of bloating, cramping, gas, and loose stools starting 1–2 hours after she drinks milk or eats ice cream. Symptoms stop when she fasts or avoids dairy. She has no weight loss or bleeding, and her tTG-IgA and CBC are normal. What is the most likely diagnosis?
IBS pain is tied to defecation and does not reliably disappear with fasting or dairy avoidance.
SIBO occurs with dysmotility, prior bowel surgery, or PPI use, and its symptoms are not tied to a single food.
Bloating, gas, and loose stools 1 to 2 hours after dairy that stop when she avoids it describe lactose malabsorption, which is very common in people of East Asian descent.
A normal tTG-IgA on a gluten-containing diet (with a normal CBC) makes celiac disease unlikely, and symptoms track dairy, not gluten.
A 23-year-old woman found a painless lump in her left breast 1 month ago that has not changed through her cycle. Examination shows a 2-cm smooth, rubbery, well-circumscribed, highly mobile mass without skin changes or axillary nodes. Targeted ultrasound shows an oval, solid, well-defined hypoechoic mass. What is the most likely diagnosis?
A smooth, rubbery, very mobile solid mass that does not change with the cycle in a woman in her 20s is most likely a fibroadenoma; ultrasound is the first imaging test under age 30.
Fibrocystic change causes tender, lumpy breasts that vary with the cycle, not a single well-circumscribed mass.
Phyllodes tumors grow quickly and are usually larger, typically in women in their 40s.
Carcinoma at 23 is rare and usually hard, irregular, and fixed, sometimes with skin or nodal changes.
A 48-year-old man who has never smoked notices a painless lump on the right side of his neck that has been present for 6 weeks. He has had no recent sore throat or dental infection. Examination shows a 3-cm soft, mobile, nontender mass below the angle of the jaw. Ultrasound shows a cystic lymph node. What is the most likely diagnosis?
Branchial cleft cysts present in children and young adults; labeling a new cystic neck mass in a 48-year-old as a branchial cyst is a dangerous error.
In an adult over 40, a persistent cystic lateral neck mass is a metastatic node from HPV-related oropharyngeal cancer until proven otherwise, even in a nonsmoker; it needs fine-needle aspiration and an ENT examination.
Thyroglossal duct cysts are midline and move with swallowing and tongue protrusion; this mass is lateral, below the angle of the jaw.
Reactive nodes follow an infection and shrink within weeks; a cystic node that persists for 6 weeks without infection is not reactive.
A 55-year-old woman has 4 months of drooping eyelids and double vision that worsen by evening, plus fatigue when chewing. Ptosis worsens with sustained upward gaze and improves after an ice pack. Acetylcholine receptor antibodies are positive. Which test should be ordered next?
CK is normal in myasthenia; it rises in myopathies such as polymyositis, which cause proximal weakness rather than fatigable ptosis.
Lumbar puncture is used for Guillain-Barré syndrome and CNS infection, not for a neuromuscular junction disorder.
Brain MRI is for stroke or demyelination; fatigable ptosis that improves with ice and positive AChR antibodies already establish MG.
Once myasthenia gravis is confirmed by acetylcholine receptor antibodies, chest CT or MRI looks for a thymoma, which is present in about 10% to 15% of patients and changes management.
A 24-year-old man has 1 week of multiple painful, shallow genital ulcers on an erythematous base, dysuria, fever, and tender bilateral inguinal lymph nodes. His first sexual contact with a new partner was 10 days ago. Several grouped vesicles are also present on the shaft. What is the most likely diagnosis?
Multiple painful shallow ulcers with grouped vesicles, fever, dysuria, and tender bilateral nodes about 10 days after exposure are a primary HSV outbreak; CDC recommends lesion NAAT plus syphilis and HIV testing.
Primary syphilis causes a single painless, indurated chancre with nontender nodes.
Chancroid causes deep, ragged, purulent painful ulcers with suppurative nodes, and grouped vesicles are not part of it.
Lymphogranuloma venereum starts with a small painless ulcer that heals before large painful inguinal buboes appear.
A 24-year-old man has had two episodes of cola-colored urine, each beginning 1 day after the start of an upper respiratory infection and clearing within a week. BP is 124/78 mmHg. Between episodes, urinalysis shows dysmorphic red cells and mild proteinuria. C3 is normal, and creatinine is normal. What is the most likely diagnosis?
Stones cause colicky flank pain and nondysmorphic red cells; they do not cause dysmorphic red cells with proteinuria after each infection.
Gross hematuria starting within a day or two of an upper respiratory infection, with dysmorphic red cells and normal C3, is IgA nephropathy.
Poststreptococcal glomerulonephritis appears 1 to 3 weeks after infection and lowers C3; episodes starting 1 day into the infection with normal C3 argue against it.
Thin basement membrane disease causes persistent, often familial, microscopic hematuria without infection-linked episodes of gross hematuria.
A 42-year-old woman presents with sudden onset of severe right eye pain, photophobia, and blurred vision for 6 hours. She wears contact lenses daily. Exam: right eye—visual acuity 20/100, conjunctival injection, corneal haze, 2 mm hypopyon visible in anterior chamber; left eye normal. Your initial impression is bacterial keratitis from contact lens overwear. To counter premature closure bias, which approach is most appropriate?
Starting drops and waiting until tomorrow anchors on bacterial keratitis and skips the same-day culture and slit-lamp exam that a hypopyon requires.
Naming alternatives (herpetic or fungal keratitis, angle closure), checking pressure, and arranging same-day ophthalmology for slit-lamp exam and culture counters premature closure.
A hypopyon in a contact lens wearer is sight-threatening; delaying the slit-lamp exam and corneal culture by days risks corneal perforation.
A normal pressure excludes angle closure but not herpetic or fungal keratitis, which need different treatment; it is not a reason to skip the specialist exam.
A 34-year-old woman with known penicillin allergy presents to urgent care with streptococcal pharyngitis confirmed by rapid antigen test. As you begin writing a prescription for azithromycin, the medical assistant mentions the patient received amoxicillin 2 months ago for sinusitis without reaction. You initially dismiss this as an error, but then pause to reconsider. What is the most appropriate immediate action to mitigate potential diagnostic bias?
Documenting the discrepancy but still choosing the second-line drug keeps the error; azithromycin also has higher streptococcal resistance.
Treating a charted label as fixed after new conflicting information is the anchoring error; most penicillin allergy labels are inaccurate.
Tolerating amoxicillin 2 months ago strongly suggests the label is wrong; asking her about the reaction and checking the record before prescribing counters anchoring and may allow first-line penicillin.
Formal testing helps when the history is unclear, but it should not delay treatment of strep pharyngitis when the history can be clarified today.
A 78-year-old woman with limited mobility presents with intermittent left lower-quadrant abdominal discomfort for 4 days. Exam shows mild tenderness without guarding. Labs and vital signs are normal. She lives alone 45 minutes from the clinic and has difficulty with transportation. The cause is not yet clear. Which safety-net plan is most appropriate given her access barriers?
Telling her the diagnosis is uncertain, naming the red flags (fever, worsening pain, vomiting, inability to eat), and scheduling a nurse phone call fits both the uncertainty and her transport barrier.
Vague reassurance without named warning signs leaves an older adult who lives alone unsure when to seek care.
Normal vital signs and labs with mild tenderness do not require emergency care today; sending her adds burden without changing the plan.
A handout with no scheduled contact relies on her to act alone; with access barriers, safety-netting needs a planned check-in.
A 27-year-old male presents to the clinic 4 hours after being struck in the right eye by a racquetball. He reports initial eye pain and tearing, now improving. Visual acuity is 20/25 right eye, 20/20 left eye. Examination reveals conjunctival injection and a small epithelial defect with fluorescein uptake. Intraocular pressure is 14 mmHg. The patient states he feels much better and requests clearance to return to play tomorrow. Which is the most appropriate next step in management?
Clearing a patient after blunt eye trauma without examining the back of the eye can miss a retinal tear, detachment, or commotio retinae.
Pain from a corneal abrasion improves quickly, so feeling better says nothing about posterior injuries from blunt force.
Blunt trauma from a ball can cause retinal tears, detachment, or commotio retinae despite improving symptoms, so a dilated fundus exam is needed before clearance.
Ointment treats the abrasion, but closing the visit without a dilated exam misses the more serious posterior injuries a racquetball can cause.
A 68-year-old woman with hypertension and diabetes woke with painless blurred vision in her left eye. Visual acuity is 20/200 on the left. Fundoscopy shows diffuse flame-shaped hemorrhages in all four quadrants, dilated tortuous veins, cotton-wool spots, and optic disc swelling. What is the most likely diagnosis?
Sudden painless loss of vision in one eye with hemorrhages in all four quadrants, dilated tortuous veins, and disc swelling is central retinal vein occlusion; hypertension and diabetes are risk factors.
Retinal detachment starts with flashes, floaters, and a curtain over the vision, and the fundus shows a detached retina rather than hemorrhages.
Proliferative diabetic retinopathy shows new vessels and is usually bilateral and gradual, not a sudden one-eye 'blood and thunder' fundus.
Central retinal artery occlusion causes sudden painless loss with a pale retina and a cherry-red spot, not widespread hemorrhages.
A 58-year-old man's wife reports 18 months of personality change: he makes crude comments to strangers, spent their savings on impulse purchases, eats sweets compulsively, and shows no concern for her feelings. He still remembers recent events and finds his way around town. He has no hallucinations or tremor. What is the most likely diagnosis?
Mania causes elevated or irritable mood, less need for sleep, and pressured speech over days to weeks, not a steady 18-month decline in social behavior.
Disinhibition, impulsive spending, loss of empathy, and a new craving for sweets with memory spared in a man under 65 are the core features of behavioral-variant frontotemporal dementia.
Alzheimer disease starts with short-term memory loss, which is preserved here.
Vascular dementia follows strokes with a stepwise decline and focal signs, which he does not have.
A 34-year-old man has had daily fevers to 39.4°C (103°F), chills, and headache for 5 days. He returned 3 weeks ago from visiting family in rural Ghana and did not take malaria prophylaxis. He appears ill; temperature is 39.1°C and the spleen tip is palpable. Which test should be obtained first?
A tuberculin skin test takes 48 to 72 hours to read and does not diagnose active disease.
Mononucleosis can cause fever and splenomegaly, but it is less likely and less dangerous here, and testing for it first delays the malaria diagnosis.
An ANA addresses autoimmune causes of prolonged fever; it does not address the life-threatening possibility in this traveler.
Fever after travel to sub-Saharan Africa without prophylaxis is falciparum malaria until proven otherwise; thick and thin smears (or a rapid test) come first and are repeated every 12 to 24 hours for three sets if negative.
A running total sits here; it fills in after your last pick.
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One patient, step two: the differential
The patient: a 58-year-old woman started lisinopril for hypertension four months ago. She now reports a dry, tickling cough of six weeks that keeps her awake. The same case runs through all four task pages. Assessment found no red flags and a normal lung examination.
ACE-inhibitor cough: dry, began after the drug was started. The leading diagnosis.
Cough-variant asthma: worse at night or with exercise or cold air.
Reflux-related cough: heartburn, worse after meals or lying down.
Post-infectious cough: follows a cold and fades over weeks.
At six weeks the cough is subacute; the CHEST guideline calls a cough chronic in adults after eight weeks. Malignancy and tuberculosis stay on the list as conditions not to miss until the history rules them down. Next step: the plan.
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Reasoning errors Diagnose items are built on
Anchoring. The first striking detail in the stem is often a decoy; reread the timeline before choosing.
Premature closure. A diagnosis that explains most findings is not good enough if one finding contradicts it.
Most likely versus most dangerous. Read which one the stem asks for; the answers differ.
Textbook picture only. Older adults often present without fever or pain (older adults).
The zebra. A rare diagnosis is a tempting distractor; choose it only when the stem supplies its specific clue.