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

When a cough lasts longer than eight weeks, it’s not just annoying-it’s a signal that something deeper is going on. Most people assume it’s just a lingering cold or allergies, but if it won’t go away, the real culprits are often three hidden conditions: GERD, asthma, and upper airway cough syndrome (formerly called postnasal drip). Together, these three cause 80 to 95% of chronic cough cases in adults who don’t smoke or take blood pressure meds like ACE inhibitors. The good news? You don’t need a dozen tests to find out what’s causing it. A smart, step-by-step approach can get you answers in weeks-not years.

Start with the basics: what your history and exam tell you

Before any scans or blood tests, your doctor should ask you the right questions. Not just, "How long have you been coughing?" but: Does it wake you up at night? Does it get worse after meals or when you lie down? Do you feel a lump in your throat or need to clear it often? Have you started a new medication recently? These details matter. A cough that shows up after eating or at bedtime? That’s classic GERD. One that flares up around pollen season or after exercise? Likely asthma. Constant throat clearing with a runny nose? That’s upper airway cough syndrome.

A physical exam isn’t just a formality. Listening to your lungs can reveal wheezing (a red flag for asthma) or silence where there should be air movement. Checking for swollen nasal passages or mucus dripping down the back of your throat helps confirm UACS. And don’t skip the chest X-ray. It’s quick, cheap, and rules out serious stuff like lung cancer or tuberculosis. If your X-ray is normal-which it usually is-you’re already in the right ballpark.

Rule out the obvious: medications and red flags

Before chasing down GERD or asthma, you need to eliminate the easy stuff. Are you taking an ACE inhibitor? Drugs like lisinopril or enalapril cause cough in up to 35% of users. The cough usually starts within a week to six months of starting the pill. Switching to a different blood pressure med can make the cough vanish in days. That’s one of the few quick fixes in chronic cough.

Then there are the red flags. If you’re coughing up blood, losing weight without trying, running fevers, or have swelling in your legs, you’re not dealing with the "big three." Those symptoms demand faster, deeper testing-like a CT scan or biopsy. But if you’re otherwise healthy and just have a persistent cough? You’re likely dealing with one of the three common causes.

Testing for asthma: it’s not always wheezing

Asthma doesn’t always come with wheezing. In fact, about one in four cases of chronic cough are caused by what’s called cough-variant asthma-where cough is the only symptom. Spirometry, a simple breathing test, is the first step. If it’s normal, that doesn’t rule out asthma. The real test? A bronchodilator challenge. You breathe in a medicine that opens your airways, then repeat the test. If your lung function improves by at least 12% and 200 milliliters, asthma is likely. Another option is a methacholine challenge: you inhale a mist that triggers airway tightening. If your lungs react strongly at low doses, you have hyperresponsive airways-classic asthma.

Treatment? Inhaled steroids and bronchodilators. Most people feel better in two to four weeks. But here’s the catch: if you’re misdiagnosed, you’ll keep coughing. That’s why the test matters. You can’t just guess.

GERD: the silent cough culprit

GERD is tricky because most people with GERD-related cough don’t have heartburn. Up to 70% of these patients never feel acid rising. It’s called silent reflux. Stomach acid travels up the esophagus and irritates the throat, triggering a cough reflex. That’s why treating it isn’t as simple as popping a Tums.

The old way? Give you a high-dose proton pump inhibitor (PPI) like omeprazole twice a day for four to eight weeks. But here’s the problem: only half to three-quarters of people respond. And guess what? About 40% of people who don’t have GERD still feel better on PPIs because of placebo effect. That’s why the American College of Gastroenterology updated its guidelines in March 2024: Don’t start PPIs without evidence. If your cough doesn’t improve after a proper trial, it’s probably not GERD.

Newer tools help. The Hull Airway Reflux Questionnaire (HARQ) scores symptoms like throat clearing, hoarseness, and post-meal cough. A score above 13 suggests laryngopharyngeal reflux with 80% accuracy. For stubborn cases, a 24-hour pH impedance test measures acid in the esophagus and throat. But it’s expensive, and insurance often won’t cover it unless you’ve tried the basics first.

Upper airway cough syndrome: the most treatable cause

This is where the old term "postnasal drip" falls short. It’s not just mucus dripping down. It’s a hypersensitive cough reflex triggered by inflammation in the nose and throat. Allergies, colds, pollution, or even dry air can set it off. The good news? This one responds best to treatment.

The diagnostic test? A trial of first-generation antihistamines (like brompheniramine) plus a decongestant (pseudoephedrine) for two to three weeks. No CT scans. No nasal sprays. Just this combo. If your cough drops by 70 to 90%, you’ve got UACS. Most people notice improvement within a week. Side effects? Drowsiness, dry mouth-but that’s why first-gen antihistamines work better than newer ones like loratadine. They cross the blood-brain barrier and calm the cough reflex directly.

Newer guidelines now call it "upper airway cough syndrome" because it’s not about drainage-it’s about nerve sensitivity. Treat the nerves, not the mucus.

The diagnostic algorithm: what order matters

There’s a reason doctors don’t start with a CT scan. The sequence matters. Here’s what works:

1. Rule out ACE inhibitors and red flags.
2. Do a chest X-ray and spirometry.
3. Try treatment for UACS first-it has the highest success rate (70-90%).
4. If that fails, try asthma treatment (inhaled steroids + bronchodilator).
5. If still no improvement, try a PPI trial for GERD.
6. If none work? Look at rarer causes: chronic aspiration, pertussis, or chronic refractory cough.

This isn’t random. UACS responds fastest. Asthma responds well. GERD is the slowest and least predictable. Jumping straight to PPIs wastes time and money. Most patients get better faster by following this order.

Why so many people get it wrong

Doctors often prescribe antibiotics for chronic cough. That’s a mistake. Less than 5% of cases are caused by bacterial infections like pertussis. And even then, you need a special nasal swab to detect it-it doesn’t show up on regular tests.

Another problem? Placebo effect. People feel better on any treatment, even if it’s not the right one. That’s why a proper trial with clear timelines matters. UACS: 1-2 weeks. Asthma: 2-4 weeks. GERD: 4-8 weeks. If you stop after a week, you’ll never know if it worked.

And then there’s the cost. A 24-hour pH test can run over $1,000. Insurance often requires prior authorization. That’s why many primary care doctors stick to the trial-and-error method. It’s practical. It’s low-risk. And when done right, it works.

What’s next? New tools on the horizon

In 2022, the FDA approved gefapixant, the first drug specifically for chronic refractory cough. It blocks a nerve signal that makes you cough. In trials, it cut cough frequency by 18-22%. A newer drug, camlipixant, showed even better results in 2024-24.7% reduction versus placebo.

AI is stepping in too. A 2023 study in Lancet Digital Health trained a machine to listen to cough sounds. It could tell asthma cough from GERD cough with 87% accuracy. Imagine a phone app that analyzes your cough at home. That’s not science fiction anymore.

The European Respiratory Society now recommends the Hull Cough Questionnaire to measure how much your cough affects your life. A score over 15 means your quality of life is seriously damaged. That’s when you know it’s time to act.

What to do if you’ve been coughing for months

If you’ve been living with a cough for over eight weeks, here’s what to ask your doctor:

• Have I been on any ACE inhibitors? If so, can I switch?
• Can we do a chest X-ray and spirometry?
• Can we try a two-week trial of an antihistamine plus decongestant?
• If that doesn’t work, can we try an inhaled steroid for asthma?
• If still no change, can we try a four-week PPI trial?

Don’t accept "It’s probably allergies" or "Just keep taking cough syrup." You deserve better. Chronic cough isn’t normal. It’s a symptom-and with the right approach, it’s fixable.