Use of cough swabs in a cystic fibrosis clinic

Abstract

We audited prospectively 322 cough swabs taken from cystic fibrosis children and compared cough swabs with concomitant sputum samples in 30 expectorating patients. A positive cough swab is a strong predictor of sputum culture. However, a negative cough swab does not rule out infection. Persistent symptoms should be further investigated. (Arch Dis Child 2001;85:438-439) Keywords: cystic fibrosis; cough swabs; sputum; clinic Over the past two decades survival has improved in cystic fibrosis (CF), mainly as a result of aggressive antibiotic policies and improved nutrition. However, death is still principally caused by respiratory failure as a result of progressive suppurative lung disease. It is increasingly realised that early recognition and eradication of airway pathogens may delay the progression of lung disease. 1 The majority of older patients expectorate and as sputum cultures accurately reflect lower airway secretions, antibiotic therapy can be tailored to the results of the sputum culture.2 Younger patients do not usually expectorate and so cough swabs from the upper airway are often used in an attempt to reflect lower airway secretions. Information on the value of routine cough swabs is scanty. The aim of this study was to audit prospectively the cough swabs taken from non-expectorating patients over a period of six months. In order to determine the diagnostic accuracy of cough swabs we compared cough swabs with spontaneously expectorated sputum samples in a separate group of 30 expectorating patients. Subjects and methodsAll non-expectorating patients attending a paediatric CF clinic (age range 1.3-17 years) over a six month period had a cough swab performed. The physiotherapist obtained cough swabs by asking the patient to cough onto a cotton tipped swab placed in, but not touching the posterior pharynx. Patients were divided into two groups, symptomatic and non-symptomatic. Patients were placed in the non-symptomatic group if they had either no respiratory symptoms or no increase in usual symptoms. In a diVerent group of 30 productive adult patients, a cough swab was taken and then sputum was spontaneously expectorated. Samples were cultured for the common CF pathogens using the following media: heated blood agar, McConkey, Burkholderia Cepacia, Difco Pseudomonas, Sabaurauds Dextrose, and mannitol salt agar. Plates were incubated at 37°C and assessed at 24 and 48 hours. Antibiotics were commenced empirically at the clinic visit according to respiratory symptoms, but treatment was altered as directed by the result of the microbiological culture.Cough swabs were compared to sputum samples using a Bland Altman two by two contingency table.3 4 ResultsA total of 322 cough swabs were obtained from 161 patients; 87 (27%) patients were symptomatic and 235 (73%) were asymptomatic. Eighteen of 235 (8%) cough swabs from asymptomatic patients were positive and isolated the following organisms: Pseudomonas aeruginosa (n = 8), Staphylococcus aureus (n = 6), Haemophilus influenzae (n = 5). All these result...

Improved early diagnosis of Pseudomonas aeruginosa by real-time PCR to prevent chronic colonisation in a paediatric cystic fibrosis population

“…However these samples poorly reflect the presence of organisms deeper in the respiratory tract and a negative cough swab does not rule out infection [12]. The use of qPCR on cough swabs as well as sputa allowed a significant improvement in the detection of P. aeruginosa over routine bacteriological culture.…”

Diagnostic accuracy and distress associated with oropharyngeal suction in cystic fibrosis

“…However, these methods have been shown to have variable diagnostic accuracy when compared to BAL [6][7][8] or expectorated sputum [9][10][11]. Furthermore, common CF pathogens are present in the upper airways of healthy children [12,13], further complicating meaningful interpretations of positive upper airway bacterial cultures.…”

Twelfth nerve palsy due to a retropharyngeal tuberculous abscess

“…In our study and the Brompton study 4 cough swabs were taken in an outpatient setting, using a method involving no direct contact with the oropharynx. The Brompton study 4 showed that cough swabs compared with sputum samples had a specificity of 100% but sensitivity of 34%. Our study showed a comparable sensitivity of 35%.…”