Chronic Cough Workup: How to Diagnose GERD, Asthma, and Postnasal Drip

Why Your Cough Won’t Go Away

If you’ve been coughing for more than eight weeks, you’re not alone. About 1 in 10 adults deal with a chronic cough that doesn’t respond to cold medicine or antibiotics. And if you’ve tried everything-antihistamines, inhalers, even cough suppressants-and still no relief, it’s probably not a cold. It’s likely one of three things: GERD, asthma, or postnasal drip. These three causes make up 80-95% of all chronic cough cases in nonsmokers who aren’t on ACE inhibitors.

Here’s the hard truth: most doctors don’t start with the right test. They prescribe cough syrup, then antibiotics, then maybe a steroid inhaler. But if the real problem is silent reflux or cough-variant asthma, those won’t fix it. The key isn’t more meds-it’s the right diagnostic path.

The Big Three: GERD, Asthma, and Upper Airway Cough Syndrome

Let’s cut through the noise. When you have a chronic cough, you’re not looking for a mystery. You’re looking for the most common culprits-and how to prove they’re the cause.

• GERD (gastroesophageal reflux disease) causes cough in 21-41% of cases. But here’s the twist: up to 70% of people with GERD-related cough have no heartburn. This is called ‘silent reflux.’ Acid creeps up, irritates the throat, and triggers coughing-especially at night or after meals.
• Asthma is responsible for 24-29% of chronic cough cases. In many, cough is the only symptom. This is called cough-variant asthma. You don’t wheeze. You don’t feel tight in the chest. You just cough-sometimes worse at night, after exercise, or around cold air.
• Upper airway cough syndrome (UACS), formerly called postnasal drip, is the most common cause, making up 38-62% of cases. It’s not just mucus dripping down your throat. It’s nerve irritation from inflammation in the nose and sinuses that makes your cough reflex go haywire.

These aren’t guesses. They’re backed by decades of research and clinical trials. The American College of Chest Physicians, the European Lung Foundation, and the American Academy of Family Physicians all agree: start here.

What Your Doctor Should Do First

Before you get a CT scan or an endoscopy, there’s a simple, safe, and cheap starting point. It’s called the minimum diagnostic workup.

1. Take a detailed history. When did the cough start? Did it begin after you started a new medication? (ACE inhibitors like lisinopril cause cough in 5-35% of users.) Does it get worse when you lie down? After eating? Around pets or pollen? Did you have a recent cold that never fully cleared?
2. Do a chest X-ray. This rules out serious stuff like lung cancer, tuberculosis, or bronchiectasis. If your X-ray is normal-which it is in 90% of chronic cough cases-you can safely focus on the big three.
3. Get spirometry. This simple breathing test checks for airflow obstruction. A normal result doesn’t rule out asthma, but a 12% and 200mL improvement in FEV1 after using a bronchodilator like albuterol confirms it. If your spirometry is normal but asthma is still suspected, a methacholine challenge test is the gold standard.

That’s it. No fancy scans. No blood tests. No expensive reflux monitors. Just history, X-ray, and breathing test. If your doctor skips these and goes straight to a CT or endoscopy, they’re not following the guidelines.

How to Test for Each Cause (Without Guessing)

Here’s where most people get stuck. They take a pill, wait a week, and if nothing changes, they assume it didn’t work. But these conditions need time-and the right treatment-to show results.

Testing for GERD

Don’t start with a pH monitor. Start with a trial. Take a high-dose proton pump inhibitor (PPI) like omeprazole 40mg twice daily for 4-8 weeks. No food 3 hours before bed. No alcohol. No caffeine after 2pm. If your cough improves by 50% or more, GERD is likely the cause.

But here’s the catch: only 50-75% of GERD-related coughs respond to PPIs. And 35-40% of people get better on placebo. That’s why the American College of Gastroenterology updated its 2024 guidelines: don’t prescribe PPIs for cough without first ruling out other causes.

For better accuracy, use the Hull Airway Reflux Questionnaire (HARQ). A score above 13 suggests laryngopharyngeal reflux with 80% sensitivity. It’s free, quick, and available at www.issc.info.

Testing for Asthma

If your cough gets worse at night, after exercise, or around cold air, asthma is a strong possibility. Spirometry is the first step. But if it’s normal, you still need a methacholine challenge test. It’s not scary-it’s a puff of mist that makes your airways react if they’re sensitive. A PC20 under 8 mg/mL means you have airway hyperresponsiveness.

Another clue? If your cough improves within 1-2 weeks of starting an inhaled corticosteroid like fluticasone, that’s a sign. You don’t need to wheeze to have asthma. Cough is often the only symptom.

Testing for Postnasal Drip (UACS)

This is the easiest to test-and the most misunderstood. You don’t need a sinus CT. You don’t need allergy tests. Just try a first-generation antihistamine (like brompheniramine or chlorpheniramine) plus a decongestant (pseudoephedrine) for 2 weeks. Take it twice daily.

Why first-gen? Because they cross the blood-brain barrier and reduce nerve sensitivity in the throat. Second-gen antihistamines like loratadine? They won’t help. Studies show 70-90% of people with true UACS improve within 1-2 weeks. If you don’t, it’s not postnasal drip.

What Doesn’t Work (And Why)

Let’s clear up some myths.

• Antibiotics for chronic cough? Almost never needed. Only 1-5% of cases are due to pertussis (whooping cough), and even then, you need a special nasal swab to detect it. Routine antibiotics won’t touch GERD, asthma, or UACS.
• Chest CT scans if your X-ray is normal? The cancer detection rate is 0.1%. The radiation exposure equals 74 chest X-rays. Not worth it unless you have red flags like weight loss, coughing blood, or night sweats.
• Over-the-counter cough syrups with dextromethorphan? They suppress the cough reflex but don’t fix the cause. You might feel better for a night, but the cough comes back.
• Ignoring medications like ACE inhibitors? If you started lisinopril six months ago and the cough began then-stop it. The cough will fade in 2-4 weeks. No other test needed.

When It’s Not One of the Big Three

Even after ruling out GERD, asthma, and UACS, 10-30% of people still have a cough. That’s when you look for the rarer causes:

• Chronic refractory cough (CRC) affects 10-20% of chronic cough patients. It’s not caused by reflux or asthma-it’s a hypersensitive cough reflex. New drugs like gefapixant (approved in 2022) and camlipixant (under FDA review) target this directly.
• Pertussis can linger for months. If you’ve been around infants or unvaccinated people, ask for a PCR test on a nasopharyngeal swab.
• Chronic aspiration happens when food or saliva goes into the lungs. Common in older adults or those with swallowing problems.
• Eosinophilic bronchitis causes cough without wheezing. Diagnosed by sputum analysis showing high eosinophils.

Don’t panic if you’re in this group. These are rare. But if you’ve tried the big three and still cough, see a pulmonologist. There are new tools now-like cough reflex sensitivity testing-that can pinpoint the issue.

What to Expect Timeline-wise

Patience matters. This isn’t a quick fix.

• UACS (postnasal drip): Improvement in 1-2 weeks with antihistamine + decongestant.
• Asthma: 2-4 weeks on an inhaled steroid before you see a drop in cough frequency.
• GERD: 4-8 weeks on high-dose PPI. Some take longer if reflux is silent.

And if you don’t respond? That’s not failure. It’s data. It means you need to dig deeper. Maybe you have two causes at once. Or maybe it’s something else.

How to Track Your Progress

Don’t just guess if you’re better. Track it.

• Use the Hull Cough Questionnaire. Score yourself before and after treatment. A drop of 5+ points means real improvement.
• Keep a simple diary: Time of day? Trigger? Severity (1-10)? Did you take your meds?
• Record your cough. Use your phone. Play it back. Is it dry? Barking? Gagging? This helps your doctor spot patterns.

One patient I worked with in Bristol kept a log for 3 weeks. She noticed her cough spiked after wine and when she slept on her back. That led to the diagnosis: silent GERD. She changed her habits-and within 5 weeks, the cough was gone.

Final Advice: Don’t Chase Tests. Chase Answers.

Chronic cough isn’t about finding the rarest cause. It’s about systematically ruling out the common ones. Most people get better by following this path:

1. Stop ACE inhibitors if you’re on them.
2. Do chest X-ray and spirometry.
3. Trial UACS treatment first (antihistamine + decongestant).
4. If no response, trial asthma (inhaled steroid).
5. If still no response, trial GERD (high-dose PPI).
6. If none work, see a specialist.

This isn’t theory. It’s what works in real clinics. And it’s backed by data from the American College of Chest Physicians, the European Lung Foundation, and over 20 years of clinical experience.

You don’t need a miracle. You need a plan. And now, you have one.