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 cough that just won’t quit. And chances are, it’s not a cold, flu, or even allergies. The real culprits are usually three quiet offenders: GERD, asthma, and postnasal drip - now more accurately called upper airway cough syndrome. Together, they cause 80 to 95% of chronic cough cases in people who don’t smoke or take ACE inhibitor blood pressure meds. But here’s the problem: none of these conditions always show up the way you’d expect. You might have GERD without heartburn. Asthma without wheezing. Postnasal drip without a runny nose. That’s why a smart workup matters - not just more tests, but the right ones, in the right order.

First, Rule Out the Red Flags

Before you even think about reflux or allergies, you need to make sure nothing serious is going on. If your cough comes with weight loss, coughing up blood, fever that won’t break, or if your doctor hears strange sounds in your lungs, you need imaging or specialist care right away. A chest X-ray is the first step for everyone with a chronic cough. If it’s normal - which it is in most cases - you’re likely dealing with one of the three common causes. But if it’s not? That’s a different story. Also, check your meds. ACE inhibitors, like lisinopril or enalapril, cause cough in 5 to 35% of people who take them. If you started coughing within weeks of beginning one of these drugs, switching to a different blood pressure pill might fix everything - no further testing needed.

The Three Big Causes: What to Look For

Once red flags are ruled out, focus on the big three. But don’t guess. Use a step-by-step approach.

1. Upper Airway Cough Syndrome (Postnasal Drip)

This is the most common cause, responsible for up to 62% of cases. It’s not just mucus dripping down your throat - it’s your airways getting irritated by inflammation in the nose or sinuses. You might not even notice nasal congestion. But you’ll likely feel the need to clear your throat, especially in the morning. The diagnostic trick? A therapeutic trial. Take a first-generation antihistamine like diphenhydramine (Benadryl) plus a decongestant like pseudoephedrine for 2 to 3 weeks. If your cough improves by 70% or more, it’s likely UACS. Response usually happens within 1 to 2 weeks. If nothing changes? Move on.

2. Asthma (Cough Variant Asthma)

One in four chronic cough cases is caused by asthma - but you might not wheeze at all. This is called cough variant asthma. It’s asthma where cough is the only symptom. Diagnosis starts with spirometry. If your lung function looks normal, the next step is a methacholine challenge test. A positive result means your airways are overly sensitive. Or, you can try a short course of inhaled corticosteroids (like fluticasone) for 4 weeks. If your cough improves by 50% or more, asthma is likely. About 24 to 29% of adults with chronic cough have this form. It’s often missed because doctors don’t think of asthma without wheezing.

3. GERD (Gastroesophageal Reflux Disease)

GERD causes cough in 21 to 41% of cases. But here’s the twist: up to 70% of people with GERD-related cough don’t have heartburn. It’s silent reflux - stomach acid reaching the throat and irritating the cough reflex. The old way was to just start a high-dose proton pump inhibitor (PPI) like omeprazole twice a day and wait. But newer guidelines warn this doesn’t work well. Only half to three-quarters of people respond. And 35 to 40% of people improve on placebo. So now, experts recommend a more targeted approach. Use the Hull Airway Reflux Questionnaire (HARQ). A score above 13 suggests laryngopharyngeal reflux with good accuracy. If you score high, try a PPI for 4 to 8 weeks - but track your cough daily. If it doesn’t improve, don’t keep taking it. You’re wasting time and risking side effects.

Why the Order Matters

Not all causes are equal. UACS and asthma respond faster to treatment - 70 to 90% of people get better with the right trial. GERD? Only 50 to 75%. So guidelines now recommend checking UACS and asthma first. If those don’t explain your cough, then move to GERD. Jumping straight to PPIs without ruling out the others leads to misdiagnosis in up to 30% of cases. You might take acid blockers for months, feel no better, and still not know why.

What Doesn’t Work (And Why)

Many people get stuck in a loop of ineffective treatments. Antibiotics? Only 1 to 5% of chronic cough cases are from bacterial infections like pertussis - and even then, you need a special nasal swab to detect it. Chest CT scans? If your X-ray is normal, the chance of finding cancer is less than 0.1%. The radiation from a CT equals 74 chest X-rays - not worth it unless something’s clearly wrong. Allergy tests? Helpful if you have nasal symptoms, but not always needed for cough alone. And don’t rely on symptoms alone. Feeling “like you have mucus” doesn’t mean you have postnasal drip. Wheezing at night doesn’t always mean asthma. Objective testing and therapeutic trials are your best tools.

What’s New in 2025

The field is changing fast. The term “postnasal drip” is being replaced with “upper airway cough syndrome” because it’s not about mucus - it’s about nerve sensitivity. New drugs like gefapixant (approved in late 2022) and camlipixant (under FDA review) target the overactive cough reflex directly. They’re not for everyone - only for those who’ve tried everything else and still cough. Also, AI tools are now being tested to analyze cough sounds. One 2023 study showed an AI could tell apart asthma-related cough from GERD-related cough with 87% accuracy just by listening. That could one day replace weeks of trial-and-error.

What You Can Do Today

Don’t wait for your doctor to suggest a workup. Be ready with this info:

1. Write down when your cough started and what makes it worse (lying down? eating? cold air?)
2. Track how often you cough each day - use a simple notebook or phone app
3. List every medication you take, especially blood pressure pills
4. Ask your doctor for a chest X-ray and spirometry
5. Ask about the HARQ questionnaire
6. Don’t accept “just take cough syrup” as an answer

If your doctor doesn’t follow the standard workup, ask why. You deserve a clear plan - not a guessing game.

What If Nothing Works?

About 10 to 30% of chronic cough cases don’t respond to treatment for the big three. That’s when you need to dig deeper. Possible causes include chronic aspiration (inhaling food or saliva), lingering effects from past infections, or chronic refractory cough (CRC) - a condition where the nerves in your airways become hypersensitive for no clear reason. Specialists now use cough reflex sensitivity tests to measure how easily your airways trigger coughing. If you’ve tried everything and still cough, ask for a referral to a pulmonologist or cough clinic. New treatments are emerging, and you’re not out of options.