【Persistent Cough? A Step-by-Step Clinical Approach to Acute and Chronic Cough】　ー　Med Student's Study Room

“I’ve had this cough that just won’t go away. It gets worse at night, and over-the-counter meds haven’t helped. I’m really starting to worry.”

Cough is one of the most common complaints in clinical practice, yet its causes can range from benign post-viral irritation to serious underlying diseases. This article will help you navigate the evaluation of both acute and chronic cough, and guide you through a structured approach from interview to investigation.

🔍 What You’ll Learn: Clinical Approach to Persistent Cough

Understand the key axes for classifying cough: acute vs. chronic, dry vs. productive, and daytime vs. nighttime variation
Learn what to ask during history-taking to narrow the differential diagnosis
Avoid missing important causes such as cough variant asthma, GERD, postnasal drip (UACS), and infections like Mycoplasma or DPB

🩺 Case : A 30s Woman with a Persistent Dry Cough

👤 Patient Profile
Age: 30s
Sex: Female

🧾 Vital Signs
Temperature: 36.8°C
SpO₂: 98% (room air)
Respiratory rate: 22 breaths/min (mildly elevated)

“I start coughing a lot at night… it’s a bit better by morning. I don’t really cough up any phlegm. I tried some over-the-counter cold meds but they didn’t help much…”

A woman in her 30s presents to clinic with a persistent dry cough lasting about two weeks. The cough is worse at night and disturbs her sleep. She reports no fever or chest pain. Over-the-counter cold and cough medications have been ineffective.

🧠 How Do You Approach This Case?

A woman in her 30s presents with a dry cough lasting about two weeks. It’s worse at night, with no phlegm, fever, or chest pain. OTC medications have not helped.

At first glance, it might seem like a lingering cold—but the pattern of nocturnal worsening and dry nature raises red flags for other conditions. Even in the absence of alarming findings on auscultation or imaging, careful history-taking can provide powerful diagnostic clues.

Let’s break down how to approach this case based on initial clinical impressions and structured classification.

🔑 Initial Classification Axes

Acute vs. Chronic

<3 weeks: Acute Cough
3–8 weeks: Subacute Cough
8 weeks: Chronic Cough

Dry vs. Productive

Dry: Suggests asthma, GERD, post-viral cough
Productive: Consider infection, bronchiectasis, chronic bronchitis

Pattern and Triggers

Nocturnal worsening: Asthma, GERD
Seasonal/Allergic: Asthma, allergic rhinitis
Positional change: GERD or bronchiectasis
Post-exertion or cold air: Reactive airway diseases

💡 Initial Clinical Impression

Based on this classification:

Dry, nocturnal cough lasting 2 weeks strongly suggests:
Cough variant asthma (CVA)
Gastroesophageal reflux disease (GERD)
Upper airway cough syndrome (UACS)
Post-infectious cough (Mycoplasma or viral)

🧭 Clinical Hypotheses to Keep in Mind

CVA: Common in younger patients; often no wheezing; nocturnal worsening
GERD: May present without heartburn; cough triggered in supine position
UACS: Especially if nasal symptoms or postnasal drip are present
Post-infectious: If a recent URI preceded the cough

The key is to let the “pattern” of the cough guide your differential. In the next step, we’ll look at how to extract targeted history using OPQRST and PAM HITS FOSS.

🗣️ Step 1: History Taking – Using OPQRST and PAM HITS FOSS

In the evaluation of cough, history-taking plays a pivotal role—especially for chronic cough, where 80–90% of diagnoses can be suspected based on a detailed interview alone.

Let’s break this step into two key components:

🔍 Symptom Analysis with OPQRST

Component	Example Questions	Diagnostic Clues
O: Onset	When did the cough start?	Acute (<3 weeks), subacute (3–8 weeks), or chronic (>8 weeks)
P: Provocation/Palliation	What makes it worse or better? (e.g., position, cold air, exertion)	Asthma, GERD, UACS, bronchiectasis
Q: Quality	Is it dry or productive? What does it sound like?	Dry: asthma, GERD; Wet: infection, COPD
R: Radiation	Any pain that goes elsewhere?	Uncommon for cough, but chest pain may suggest complications
S: Severity	Does it interfere with sleep or daily activities?	Disabling cough suggests need for intervention
T: Timing	Is it worse at night, in the morning, or seasonal?	Night: CVA/GERD; Morning: bronchitis/COPD

🧾 Background Factors: PAM HITS FOSS

Each element of the acronym helps uncover hidden triggers or risk factors.

Category	Focused Questions	Key Associations
P: Past history	Asthma, sinusitis, GERD, chronic bronchitis?	CVA, UACS, DPB
A: Allergies	Known allergies (pollen, dust, pets)?	Asthma, allergic rhinitis
M: Medications	On ACE inhibitors or beta blockers?	Drug-induced cough
H: Hospitalization	Did the cough improve during hospital stays?	Hypersensitivity pneumonitis
I: Immunization	Pertussis or flu vaccine updated?	Pertussis-like illness
T: Travel	Recent travel to TB-endemic areas?	TB, non-TB mycobacteria
S: Sick contacts	Anyone around you sick recently?	Viral/bacterial infection
F: Family history	Any asthma or autoimmune diseases?	Atopic predisposition
O: Occupation	Exposed to chemicals, dust, animals?	Occupational lung disease
S: Social history	Smoking or passive smoke exposure?	COPD, chronic bronchitis
S: Substance use	OTC meds or herbal remedies used?	Masked symptoms or delayed care

To deepen your assessment, consider these additional tools and red flags that enhance diagnostic accuracy:

🧪 Patterns and Triggers of Cough

Pattern or Trigger	Possible Diagnosis
Worse at night	Cough variant asthma (CVA), GERD
Morning-predominant	COPD, chronic bronchitis
Exacerbated by cold air or exercise	Asthma, allergic rhinitis
Postural change (e.g. lying down)	GERD, bronchiectasis
Post-infectious lingering dry cough	Viral illness, Mycoplasma, CVA
Improves during hospitalization	Hypersensitivity pneumonitis
Absent during sleep	Psychogenic cough

💬 Sputum Characteristics (If Present)

Color: yellow/green → infection, pink frothy → heart failure
Amount: cups per day can help quantify severity (e.g. bronchiectasis)
Odor: foul-smelling sputum may indicate anaerobic infection or abscess

🎧 Cough Sound Qualities

Barking (seal-like): Pertussis or tracheal inflammation
Metallic: Laryngeal lesions
Inspiratory whoop: Classic for pertussis
Stridor: Upper airway obstruction

📋 Useful Assessment Tools for Chronic Cough

Leicester Cough Questionnaire (LCQ): QOL-focused tool assessing physical, social, and emotional impact. University of Leicester – Download
ATS Chronic Cough Guidelines: Evidence-based flowcharts by the American Thoracic Society. Download the official PDF
ERS Patient Perspective Tool: From the European Respiratory Society; emphasizes subjective impact and symptom tracking. Read the ERS Guidelines (2020)

A structured history like this not only guides your differential diagnosis but also prepares you to refer patients appropriately when needed. Next, we’ll move on to the physical examination—what to look for, and how to interpret it.

🩺 Step 2: Physical Examination – Systematic Respiratory Evaluation

Physical exam in patients with persistent cough begins the moment the patient walks into the room. Clues such as voice quality, posture, breathing effort, and the character of the cough itself can offer critical diagnostic insights—even before the stethoscope comes out.

Here’s how to approach it in a structured and high-yield way:

👀 General Appearance and Vital Signs

Fever, tachypnea, hypoxia, altered mental status → Think pneumonia, asthma exacerbation, or anaphylaxis
Posture, work of breathing (e.g., use of accessory muscles, nasal flaring)
Facial features and body habitus can offer indirect clues:
“Blue Bloater”: Obese, cyanotic, productive cough → chronic bronchitis-type COPD
“Pink Puffer”: Thin, pursed-lip breathing, dry cough → emphysematous COPD

🎧 Auscultation: Interpreting Lung Sounds

Auscultation Finding	Description	Possible Diagnoses	Suggestive Site
Wheeze	High-pitched, musical, often expiratory	Asthma, COPD	Bronchi / Small airways
Rhonchi	Low-pitched, snoring-like	Bronchitis, secretions	Large airways
Fine crackles	Soft, high-frequency at end-inspiration	Interstitial lung disease, heart failure	Alveoli
Coarse crackles	Louder, wet-sounding	Pneumonia, bronchiectasis	Bronchial and alveolar
Stridor	Harsh inspiratory sound	Upper airway obstruction, anaphylaxis	Larynx / Trachea

🔸 Tip: Dry coughs → wheeze or fine crackles; Wet coughs → rhonchi or coarse crackles.

🧩 Additional Clues Outside the Chest

Nasal discharge or postnasal drip → Suggests UACS
Throat erythema or cobblestoning → UACS or GERD
Epigastric tenderness, acid reflux on palpation → GERD
Dullness to percussion → Pleural effusion
Hyperresonance → Pneumothorax
Rash, conjunctivitis, joint swelling → Systemic diseases (e.g., vasculitis, sarcoidosis)

🚨 Don’t Miss: Anaphylaxis as a Cause of Cough

Cough may be one of the earliest signs of anaphylaxis
Look for stridor, wheezing, hoarseness
If suspected: administer IM epinephrine immediately

Physical examination doesn’t just confirm suspicion—it often redirects or refines your hypotheses. In the next step, we’ll discuss how to select investigations that truly matter.

🧪 Step 3: Investigations – Targeted Tests Based on Hypotheses

After a structured history and physical examination, the next step is to test your hypotheses—selectively and strategically.

Rather than ordering a broad battery of tests, think: What am I trying to rule in or out? Use each investigation to either confirm a likely diagnosis or confidently exclude serious pathology.

🩸 1. Blood Tests – Inflammation, Allergy, Systemic Clues

Test	Purpose	Conditions Suggested
CBC (with eosinophils)	Infection or eosinophilic inflammation	Pneumonia, asthma, eosinophilic lung disease
CRP / PCT	Acute bacterial infection vs. non-infectious causes	Pneumonia, bronchitis
Total IgE, RAST	Atopic tendency, specific allergens	Asthma, UACS
BNP	Cardiac-related cough	Heart failure
ANA / Anti-CCP	Autoimmune screen	ILD, vasculitis, connective tissue disease

🩻 2. Imaging – CXR First, Then CT if Needed

Chest X-ray (CXR): The first-line test for most cough patients
Screens for pneumonia, effusion, tumor, atelectasis
Note: often normal in CVA, GERD, or postnasal drip
Chest CT (HRCT): Use when CXR is abnormal or suspicion remains
Interstitial lung disease, bronchiectasis, tumors, hypersensitivity pneumonitis

🌬 3. Pulmonary Function & Sputum Tests – For Chronic or Recurrent Cases

Spirometry with bronchodilator test: Obstructive patterns in asthma or COPD
FeNO (exhaled nitric oxide): Marker of eosinophilic airway inflammation; elevated in CVA
Sputum Gram stain and culture: Useful if productive cough or recurrent infections

🩻 4. POCUS (Point-of-Care Ultrasound) – Quick Bedside Clues

Pleural effusion: Identify and characterize effusion
B-lines / lung rockets: Suggest interstitial edema → heart failure
RV strain or dilation: Consider pulmonary hypertension, PE

🚫 Avoid Over-Testing: Common Pitfalls

High CRP ≠ always bacterial → consider viral, non-infectious causes
Normal CXR ≠ no disease → asthma, GERD, and UACS may be radiologically silent
Rule out drug-induced causes (ACE inhibitors) and environmental triggers first

🧭 Testing Strategy by Clinical Pattern

Clinical Clue	Suggested Test
Dry, nighttime cough	FeNO, spirometry → suspect CVA
Wet cough with purulence	CXR + sputum culture
Recurrent or progressive course	HRCT for ILD, bronchiectasis

🔬 Special Considerations for Atypical or Rare Conditions

Mycoplasma pneumonia:
Cold agglutinins may be positive (low sensitivity)
Diffuse CXR infiltrates despite mild symptoms
Diffuse Panbronchiolitis (DPB):
Check for chronic sinusitis history
HRCT: centrilobular nodules, tree-in-bud, mosaic attenuation
H. influenzae often cultured from sputum
Hypersensitivity pneumonitis:
Key: Exposure history and symptom relief during hospital stay
HRCT: ground-glass opacities, centrilobular nodules
Chronic forms may show fibrotic changes

By linking your diagnostic hypotheses to test choices, you can streamline care, avoid overtesting, and reach diagnoses more efficiently.

In the next section, we’ll apply these principles to our case example.

🔄 Let’s Apply This to Our Case

Now that we’ve reviewed Steps 1 through 3, let’s return to the original clinical vignette and walk through how each step would unfold in real practice.

👣 Step 1: History Taking

👨‍⚕️ Doctor: What brings you in today?

👩 Patient: I’ve had this dry cough for about two weeks. It gets worse at night, and I can’t sleep well.

👨‍⚕️: Do you bring up any phlegm? What does your cough sound like?

👩: No, it’s mostly dry. It’s kind of a scratchy, tickling cough.

👨‍⚕️: Any fever, sore throat, or nasal symptoms?

👩: I had a bit of sore throat the first couple of days, but now it’s just the cough.

👨‍⚕️: Have you had anything like this before?

👩: Yeah… last winter I had a similar cough that lasted a few weeks.

👨‍⚕️: Any allergies or regular medications?

👩: No allergies and I’m not on any meds.

📝 Summary:

Fact: Persistent dry cough for 2 weeks, worse at night, no sputum, no systemic signs
Problem: Subacute, dry, nocturnally worsening cough with past similar episodes
Hypotheses: Cough variant asthma (CVA), GERD, postnasal drip (UACS), early asthma

🩺 Step 2: Physical Examination

Auscultation: Mild wheezes bilaterally, no rhonchi or crackles
Vitals: Normal RR, SpO₂, and temp
No signs of infection: No nasal discharge, no throat erythema, no lymphadenopathy
No postnasal drip or sinus tenderness

➡️ Interpretation: No red flags. Wheezing and normal vitals support CVA as the leading possibility.

🧪 Step 3: Investigations

CBC: Normal WBC, mild eosinophilia
CRP / PCT: Within normal limits
CXR: Normal
FeNO: Elevated (45 ppb)

➡️ Interpretation: Inflammatory airway pattern without infection or structural findings.

🎯 Conclusion: Most consistent with Cough Variant Asthma. Initiate ICS ± LTRA and follow-up.

This case illustrates how even without overt systemic findings, structured reasoning can guide you toward a confident diagnosis.

Next, we’ll discuss when to refer patients with persistent cough to specialists and what evaluations should be done beforehand.

When to Refer Chronic Cough – Criteria and Pre-Referral Checklist

Not all coughs require specialist referral, but knowing when to escalate is crucial—especially for cases that persist despite treatment, show red flags, or suggest complex underlying disease.

Here’s a practical guide to when and how to refer:

📌 Indications for Referral

Consider referring to a pulmonologist or relevant specialist when:

Cough persists beyond 8 weeks despite adequate primary care evaluation
Chest imaging (CXR or HRCT) shows abnormalities requiring further workup
Suspected asthma, CVA, or GERD does not respond to standard treatment
There is a suspicion of interstitial lung disease (ILD) or hypersensitivity pneumonitis
Cough is severely impacting QOL or associated with weight loss, hemoptysis, or clubbing

🧾 Workup to Complete Before Referral

Referring physicians can greatly help specialists by ensuring some basic evaluations are done beforehand:

Domain	Recommended Tests or Notes
Imaging	Chest X-ray (mandatory); HRCT if red flags or unresolved findings
Sputum	Gram stain and culture for wet, persistent cough
Lung function	Spirometry ± bronchodilator response; FeNO if available
Allergy testing	Total IgE, RAST (esp. if asthma/UACS suspected)
Clinical records	Symptom onset, patterns, treatment response, prior episodes

✍️ What to Include in the Referral Letter

Clear summary of symptom onset, duration, and progression
What diagnoses were considered and ruled in/out
Treatments already tried and their effects
Whether there is impact on work, sleep, or ADLs
What support or next steps you are requesting from the specialist

🔑 Remember: Referral is not about “giving up,” but about collaborative care. A thoughtful handover ensures that no steps are repeated and that the specialist can pick up where you left off.

In the next section, we’ll focus on OET-specific strategies—both writing and speaking—that are particularly useful for managing and communicating about cough cases.

✍️ OET Strategy: Writing and Speaking for Cough Cases

Mastering clinical communication around cough not only improves patient care—it’s also key for OET success. Below are practical expressions and strategies tailored for OET Writing and Speaking sub-tests.

📄 OET Writing: Referral Letter Tips

When writing about a patient with persistent cough, your letter should demonstrate structured reasoning and clear communication of the clinical picture. Here are some model phrases:

Describing the patient’s history:

“Ms. Jones, a 35-year-old woman, has presented with a two-week history of a persistent dry cough, predominantly nocturnal in nature.”
“Her symptoms have not improved with over-the-counter medications and are now affecting her sleep quality.”

Indicating your working diagnosis or concern:

“Based on the clinical course and elevated FeNO levels, cough variant asthma is the leading differential.”
“Although the chest X-ray was unremarkable, the persistent nocturnal cough raises concern for underlying GERD.”

Requesting further management:

“I would appreciate your assessment and consideration for pulmonary function testing.”
“Your opinion on initiating ICS therapy or allergy testing would be valuable.”

📝 Sample Referral Letter (OET Writing)

Writing Task Example:

You are a GP. A 35-year-old woman visited your clinic today complaining of a dry cough that has persisted for two weeks. You suspect cough variant asthma. Write a referral letter to Dr. Susan Bell, a respiratory specialist at City Hospital, for further evaluation.

Sample Letter:

21 June 2025
Dr. Susan Bell
Respiratory Medicine Department
City Hospital

Dear Dr. Bell,

I am writing to refer Ms. Rachel Jones, a 35-year-old patient, who has presented with a two-week history of a persistent dry cough that is worse at night and unresponsive to over-the-counter medication.

Ms. Jones reports no fever, sputum production, or chest pain. Physical examination revealed mild expiratory wheezing. Chest X-ray findings were normal. Notably, her FeNO level was elevated (45 ppb), and blood tests showed mild eosinophilia.

Her symptoms and test results strongly suggest a diagnosis of cough variant asthma. I have not initiated inhaled corticosteroids at this stage and would appreciate your assessment and consideration for initiating pharmacologic therapy and further workup as needed.

If you require additional information, please do not hesitate to contact me.

Yours sincerely,
Dr. ***
General Practitioner

🗣️ OET Speaking: Explaining Cough-Related Conditions

Describing diagnoses in plain English:

“It looks like your cough might be related to a form of asthma that mainly causes coughing, especially at night.”
“Sometimes, stomach acid can come up and irritate the throat, leading to a dry cough. This is called reflux.”

Answering challenging questions from the patient:

Q: “Why am I not getting better with cough syrup?”
A: “That’s a good question. Cough syrups often don’t work well for this type of cough, because the cause is not just throat irritation—it may be related to your airways or even your stomach.”
Q: “Do I need a chest X-ray?”
A: “In your case, your symptoms suggest inflammation in the airways rather than an infection or tumor, so an X-ray may not be necessary right away.”
Q: “Could it be something serious?”
A: “From what we’ve seen so far, there are no signs pointing to anything serious like cancer or pneumonia, but we’ll keep monitoring and do further tests if needed.”

These expressions help you strike a balance between clinical clarity and patient-friendly language—exactly what the OET assesses.

Next, we’ll highlight practical clinical tips for history taking and physical examination—followed by a few memorable clinical pearls to guide your reasoning in real practice.

💡 Clinical Tips – History and Examination Strategies

These practical tips help sharpen your diagnostic edge when dealing with patients presenting with cough:

Always start by clarifying whether the cough is dry or productive—this shapes your entire differential.
Ask about nocturnal or early morning worsening to differentiate between CVA, GERD, and chronic bronchitis.
Inquire about triggers like exercise, cold air, or lying down.
Consider occupational and environmental exposures—especially if symptoms improve during hospitalization.
Don’t overlook past similar episodes: recurrent patterns suggest CVA or post-infectious cough.
During auscultation, compare both sides and listen after coughing—it can reveal transient wheezes or clearing rhonchi.
Observe breathing style and body habitus: e.g., Blue Bloater vs. Pink Puffer patterns in COPD.

🧠 Clinical Pearls – Memorable Quotes for Clinical Reasoning

“Cough is the common cold’s last goodbye.”
→ A lingering cough may still be benign, but don’t assume—it could mask something more serious.

“Not all wheezes are asthma, and not all asthma wheezes.”
→ Lack of wheezing doesn’t rule out asthma. Listen with an open mind.

“Chronic cough is often more about what you don’t hear than what you do.”
→ Silence can be misleading; radiologically normal doesn’t mean clinically silent.

Next, let’s summarize the key takeaways from this clinical approach to cough.

📝 Summary – Clinical Approach to Cough

Cough is a common but deceptively complex symptom. Its causes span across respiratory, gastrointestinal, and even cardiovascular domains. Through this article, we’ve broken down a step-by-step strategy for evaluating both acute and chronic cough—from structured history-taking and physical exam to targeted investigations.

Key takeaways:

Classify cough based on duration, quality, and triggers (e.g., nocturnal, positional)
Use OPQRST and PAM HITS FOSS to explore history thoroughly
Physical exam begins with observation—listen, look, and sense for subtle patterns
Investigations should be hypothesis-driven—avoid overtesting, but don’t miss red flags
Remember atypical but important causes like CVA, GERD, UACS, DPB, and hypersensitivity pneumonitis
Communicate clearly: whether in clinic or OET exam, your reasoning should be structured, logical, and patient-centered

Sometimes, a cough is “just a cough”—but other times, it speaks for something deeper. Keep your differential broad, your tools sharp, and your ears open.

Looking to strengthen your medical English? Check out our other bilingual articles in the Symptom-Based Clinical Approach series.

👉 Prefer to read in Japanese? 【咳が止まらない原因は？急性・慢性咳嗽の診断と診療アプローチ】はこちらから。

📚 References

Japanese Respiratory Society. Guidelines for the Management of Cough (2022)
Morice AH et al. ERS guidelines on the diagnosis and treatment of chronic cough in adults and children. Eur Respir J. 2020.
Pratter MR. Overview of common causes of chronic cough: ACCP evidence-based clinical practice guidelines. Chest. 2006.
Yousaf N, et al. Chronic cough: an Asian perspective. Cough. 2011.