Guideline 59 - Supporting Material

Community Management of Lower Respiratory Tract Infection in Adults

A recent UK study¹ of the incidence of lower respiratory tract symptoms in previously well adults in the community used the following definition of their illness:

• An acute illness present for 21 days or less
• Cough as the cardinal symptom
• At least one other lower respiratory tract symptom (sputum production, dyspnea, wheeze, chest discomfort)
• No alternative explanation e.g. not sinusitis, pharyngitis or asthma.

This study failed to identify an infectious agent for the symptoms in over 45% of patients (Table 1) and suggested that while Streptococcus pneumoniae remains a common cause of LRTI, the atypical organism, Chlamydia pneumoniae, appears to be equally as common.¹

Positive identification of an antibiotic sensitive organism only occurs in a minority of cases when previously well adults present with lower respiratory tract symptoms.

Table 1

Infectious agents isolated from previously well patients with LRTI symptoms

‡: 316 subjects (over 16 years of age) studied for 12 months.¹

As can be seen from the table above, organisms other than bacteria (such as viruses, Chlamydia and Mycoplasma) are probably responsible for a large proportion of community acquired LRTI, including both pneumonia and exacerbations of COPD.

The mainstay of chlamydia diagnosis is serology and there are three assays available. A positive result in a patient with appropriate signs should lead to introduction of appropriate antibiotics.

Mycoplasma pneumoniae infections occur every year, but there are epidemics every 3-4 years. During such epidemics, it is a common cause of community acquired LRTI.¹ Chlamydia and Mycoplasma polymerase chain reaction (PCR) assays are under development, but at present are not reliable enough to replace serology.

Viral causes of LRTI are currently underdiagnosed and include members of the Picornavirus family (enteroviruses and rhinoviruses); influenza viruses A and B; parainfluenza viruses 1, 2 and 3; coronaviruses; adenoviruses; and respiratory syncytial virus (RSV). Much work has been done on these agents as precipitants of asthma, in children and adults. About 80% of attacks in children and over 50% in adults were associated with these agents.^2,3 Approximately a third of exacerbations of COPD are thought to be linked to a virus infection, but data are limited. There is a need for further work in this area.

Current approaches for virus diagnosis include serology, which is usually not positive during the illness and is not able to detect antibodies against all viral pathogens (for example, rhinovirus and coronavirus).

Direct fluorescence and virus culture are difficult to apply to large numbers of people. Recently, molecular PCR detection techniques have become available and have a high sensitivity and a short turn round time.² For example, the detection of rhinoviruses is increased 5-6 fold, adenovirus 2-3 fold and influenza PCR is 20-30% more sensitive than culture. One of the benefits of the introduction of these assays has been the insight into the role of rhinoviruses in serious respiratory conditions. Previously thought to be trivial causes of the common cold, they can be regularly found in patients with asthma, immunosuppressed patients with pneumonia and other LRTI.^4,5 The Scottish Executive has funded the Scottish Enhanced Respiratory Viral Infection Surveillance scheme, which CMR practices can join. Swabs are submitted to the Regional Virus Laboratory in Glasgow and results faxed back the next day. Over the 2000/2001 season, approximately 1100 swabs were submitted, of which 40% had a virus detected. A total of 12% were influenza, 17% rhinovirus and 8% RSV.

Currently, these PCR assays are performed in one laboratory in Scotland and are not yet widely available.

References

1 Macfarlane J, Holmes W, Gard P, Macfarlane R, Rose D, Weston V et al. Prospective study of the incidence, aetiology and outcome of adult lower respiratory tract illness in the community. Thorax 2001; 56: 109-14.

2 Freymuth F, Vabret A, Brouard J, Toutain F, Verdon R, Petitjean J et al. Detection of viral Chlamydia pneumoniae and Mycoplasma pneumoniae infections in exacerbations of asthma in children. J Clin Virol 1999; 13: 131-9.

3 Atmar RL, Guy E, Guntupalli KK, Zimmerman JL, Bandi VD, Baxter BD et al. Respiratory tract viral infections in inner-city asthmatic adults. Arch Intern Med 1998; 158: 2453-9.

4 Malcolm E, Arruda E, Hayden FG, Kaiser L. Clinical features of patients with acute respiratory illness and rhinovirus in their bonchoalveolar lavages. J Clin Virol 2001; 21: 9-16.

5 Papadopoulos NG, Johnston SL. Rhinoviruses as pathogens of the lower respiratory tract. Can Respir J 2000; 5: 409-14.