Chronic Cough in Adults: What's the Diagnosis?

Dr Jessica Garner Considers Some Possible Causes of Chronic Cough and Describes the Tests Used to Diagnose or Eliminate a Range of Conditions

Chronic cough is one of the most common presentations seen in general practice, with the condition affecting between 10% and 20% of the population.^1,2 Chronic cough is defined as a cough lasting longer than 8 weeks and it can cause significant impairment to quality of life.³ There are numerous causes of chronic cough and a clear history is vital in guiding further management. Important risk factors include smoking and a history of atopy. Drug history is also important since a number of common drugs, such as angiotensin converting enzyme inhibitors, can precipitate cough.² Occupational and travel history are also important and should not be neglected.

Given the vast number of patients who present each year with cough symptoms, it is important to be able to differentiate a cough due to serious underlying pathology from more benign disease. Box 1 lists ‘red flags’ that would warrant prompt investigation and appropriate management.

Case 1

A 37-year-old woman presents with a 4-month history of a dry cough. The cough is worse at night, often causing her to wake up, and is more noticeable in cold weather. She has a history of hayfever and her brother had childhood asthma. She is a keen runner and has noticed that over the last few months she has found it more difficult to train than usual. She works as a high school teacher and is not on any regular medication. She has no known allergies, is a non-smoker, and has no pets. On examination she is well and her chest is clear. A peak flow reading gives a result of 65% of predicted value.

Diagnosis

Given the patient’s history, a diagnosis of asthma is high on the list of possible diagnoses. NICE Guideline (NG) 80 on Asthma: diagnosis, monitoring and chronic asthma management⁶ recommends that all patients with suspected asthma should be offered objective testing for the disease, rather than relying purely on a convincing history. Fractional exhaled nitric oxide (FeNO) testing should be carried out as first-line diagnostic testing, in conjunction with spirometry (see Box 2).⁶

Should tests result in an uncertain diagnosis, a 2–4-week period of serial measurement of peak flow may be helpful. Variability of more than 20% is regarded as diagnostic. Should a diagnosis of asthma still be in doubt, despite a convincing history and supportive clinical examination, direct bronchial challenge testing with histamine or methacholine can also be used to test for airway hyperactivity. Should these results be negative or inconclusive, an alternative diagnosis should be considered or the patient referred to secondary care. Interestingly, if direct bronchial challenge testing is unavailable, treating the patient as if they had asthma and monitoring improvement is appropriate.⁶

Management

Given that the patient is having persistent symptoms and waking up at night several times a week, it is reasonable to start her on a low-dose inhaled corticosteroid (ICS) along with a short-acting beta₂ -agonist (SABA).⁶ A review 4–8 weeks later would be appropriate to monitor symptoms. Adding a leukotriene receptor antagonist (LTRA), followed by the introduction of a long-acting beta₂ -agonist (LABA), are the next appropriate steps. Should symptom control be difficult to achieve on low-dose ICS plus a LTRA and/or a LABA, the dose of ICS can be carefully titrated upwards.⁶

Outcome

The patient’s FeNO and spirometry tests confirmed a diagnosis of asthma. She was treated with a low-dose ICS and an as-required short-acting beta₂ -agonist. Within 4 weeks her symptoms had markedly improved. She only required salbutamol when running in cold weather, and her nocturnal cough had completely gone. She attends for asthma reviews regularly and is aware of when to seek help should her symptoms deteriorate.

Case 2

A 48-year-old man presents to the surgery with a 9-week history of a dry cough. He has noticed that the cough is worse after eating, but can occur at any time of the day. He spent the weekend doing DIY which required much bending over, and his cough became much more noticeable. He describes mild dyspepsia after eating, which started approximately 4 months ago. Examination is unremarkable other than mild epigastric tenderness on palpation and a BMI of 38 kg/m².

Diagnosis

Gastro-oesophageal reflux disease (GORD) is a well-recognised cause of chronic cough. Although other symptoms of GORD may be present, these may be mild or even absent in up to 75% of cases.⁷ The mechanisms behind GORD-induced cough are thought to be a result of either microaspiration of gastric contents and/or a vagally mediated oesophageal-tracheobronchial reflex.^7,8 Food intake, as well as a number of medications (such as non-steroidal anti-inflammatory drugs and theophylline), can aggravate GORD, as can posture including lying supine.⁷

Management

Given the clinical suspicion of GORD, in the absence of any red flag symptoms, an initial 4-week course of a proton pump inhibitor (PPI) can be offered.⁹ Lifestyle advice regarding weight loss is also appropriate for patients with a BMI over 25 kg/m².⁹ If symptoms persist, the patient should be tested for Helicobacter pylori infection with a breath test or a stool antigen test, after a 2-week washout period from the PPI.⁹

Outcome

The patient returned for a review appointment 1 month later and reported that his cough had improved significantly. He still experienced a mild cough after heavy meals but otherwise felt much better. He had intentionally lost half a stone in weight and aimed to continue his healthy lifestyle. Because of the ongoing presence of mild symptoms, he was tested for H. pylori; test results were positive so triple therapy (a PPI, amoxicillin, and either clarithromycin or metronidazole⁹) was prescribed. Following treatment his symptoms resolved.

Case 3

A 39-year-old IT consultant attends with an irritating cough, which has been present on and off for 4 months. For the past 6 weeks it has been occurring on a daily basis and he is concerned he may have an underlying serious pathology. On further questioning, the cough is largely non-productive other than first thing in the morning when he expectorates sputum. His partner has noticed that he appears to be constantly clearing his throat and he has noticed the sensation of something dripping down the back of his throat. The symptoms started after a cold but have persisted since then. He is an ex-smoker, having stopped 6 years ago. He drinks moderate amounts of alcohol and has mild hay fever.

Diagnosis

This patient’s symptoms are characteristic of postnasal drip (PND). Postnasal drip, or upper airway cough syndrome as it is also known, is the drainage of secretions from the nose or paranasal sinuses into the pharynx. Multiple studies have suggested that it is the most common cause for a chronic cough.¹⁰ Postnasal drip is largely diagnosed by a typical history of the sensation of having something drip down into the throat, nasal discharge, frequent throat clearing, and cough;¹⁰ however, it can be diagnostically challenging as there are no objective tests for it and no way to quantify the amount of PND.

The differential diagnoses of PND include all other causes of rhinitis, such as allergic rhinitis, bacterial sinusitis, allergic fungal sinusitis, rhinitis due to anatomic sinonasal abnormalities, rhinitis due to physical or chemical irritants, occupational rhinitis, rhinitis medicamentosa, and rhinitis of pregnancy. A careful history can help differentiate between these various aetiologies.^11,12 The issues of PND are further complicated by the fact that GORD can often co-exist with or mimic PND.¹²

In this case a full examination would be advised. There may be a nasal quality to the voice because of concomitant nasal blockage and congestion, and there may be hoarseness of the voice. Physical examination of the pharynx is often unremarkable, although a ‘cobblestoning’ appearance of the mucosa and draining secretions may be observed.¹³ Given the patient’s history of smoking and presence of chronic cough, a baseline chest radiograph would be recommended as per British Thoracic Society guidance.²

Management

Treatment of postnasal drip with a trial of topical corticosteroids is not only therapeutic but, given the difficulties in confirming the syndrome, can be of diagnostic importance. The patient should be warned that resolution of symptoms can take several weeks and occasionally months.¹² Anecdotally, many clinicians will try a number of topical corticosteroids should the first-line option fail to improve symptoms. If there is a history of potential allergy, non-sedating antihistamines can be used in addition to a topical corticosteroid.¹² Care should be taken with decongestants because of the risk of rebound symptoms and rhinitis medicamentosa with prolonged use.¹⁴

Outcome

The patient was given 1-month trial of a low-dose over-the-counter topical steroid. He presented 4 weeks later complaining that his symptoms had failed to improve. He was switched to an alternative nasal spray and good compliance was urged. He presented 6 weeks later delighted that his symptoms had settled and both the cough and clearing of his throat had improved. He continued the topical treatment for a total of 3 months before ceasing medication altogether.

Case 4

A 72-year-old woman presents with a 6-month history of chronic dry cough and increasing breathlessness. She has been treated periodically for chest infections over the past few months. Her breathlessness is beginning to make walking upstairs or on an incline difficult. She does not think she has lost any weight and is not on any regular medications. She has never smoked and is a retired GP receptionist. On examination she has bibasal inspiratory crackles. A chest X-ray is arranged, which is abnormal.

Diagnosis

This woman may have underlying pulmonary fibrosis. Pulmonary fibrosis may be secondary to a wide range of diseases; however, one of the most common types is idiopathic which affects approximately 10 per 100,000 people in the UK each year.^15,16 Idiopathic pulmonary fibrosis rarely affects people under the age of 45 years and typically presents with breathlessness on exertion, a dry cough, bilateral inspiratory crackles, and clubbing of the fingers. Patients can also exhibit non-specific constitutional symptoms such as myalgia, fatigue, or weight loss. In the later stages of disease, cyanosis and features of right heart failure commonly occur.¹⁷ Given this patient’s history and abnormal chest radiograph, a high-resolution computed tomography of her chest is arranged, revealing a typical honeycombing appearance typical of idiopathic pulmonary fibrosis.¹⁸ She has baseline spirometry at the practice, which reveals a restrictive pattern, and so is referred to the respiratory multidisciplinary team.

Management

Following the patient’s diagnosis, her future management and prognosis should be sensitively discussed. It is important to explain that, other than lung transplantation, there is no cure for the disease and medication is often ineffective. The median survival for idiopathic pulmonary fibrosis in the UK is approximately 3 years, although up to 20% of people survive for 5 years or more. For this reason good palliative care, even at an early stage, is vital in the management of pulmonary fibrosis.¹⁹ The respiratory team arranged for this patient to start pulmonary rehabilitation with regular review on a 6-monthly basis.²⁰

Outcome

About 1 year after the patient’s diagnosis her health started to deteriorate more rapidly and her spirometry and gas exchange dropped. Home oxygen was initiated and a sensitive discussion about the poor outcomes associated with both mechanical ventilation and resuscitation was had with the patient and her family. She continued to decline rapidly and full palliative care support was provided. She died at home 6 months later.

Conclusion

Chronic cough is a common symptom encountered in general practice. A full history and examination will help to identify the possible causes of cough. Further investigations in the form of lung function tests, testing for the presence of H pylori, chest radiography, and trials of medicines such as PPIs and topical corticosteroids are used to confirm the diagnosis. Treatment and management can be instigated in primary care but patients may need referral to secondary care if test results are inconclusive or if diagnosis reveals conditions such as idiopathic pulmonary fibrosis, which require specialist management.

Dr Jessica Garner

GP, Worcester