Amanda J Cox(1), Maree Gleeson(2), David B Pyne(1), Robin Callister(2), Will G Hopkins(3), Peter A Fricker(4) 
1 Physiology, Australian Institute of Sport
2 University of Newcastle
3 Auckland University of Technology, New Zealand
4 Australian Institute of Sport

Background
Upper respiratory tract infection (URTI) is the most common infectious illness reported in elite athletes. However, the appearance of respiratory symptoms in athletes most likely involves both infectious and non-infectious causes, and the automatic classification of upper respiratory symptoms (URS) as URTI can be misleading, failing to accurately identify other possible causes. Accurate evaluation of URS in athletes is important to allow administration of appropriate treatment and management strategies, particularly where symptoms result from causes other than infection and more long-term management may be required.

Aim
The aim of the current study was therefore to characterise the etiology of upper respiratory symptoms in elite athletes presenting to a sports physician for treatment.

Methods
Seventy elite level athletes were recruited to the study on presentation to the sports medicine clinic with respiratory symptoms. Physician-recorded symptoms and diagnosis were noted and participants completed health and training questionnaires by interview with the main researcher. Blood and saliva samples were collected for a series of laboratory investigations including detection of respiratory pathogens, differential white blood cell counts and immune parameters.

Results
Physicians characterized 89% of presentations as viral or bacterial upper respiratory tract infection. In contrast, only 57% of presentations were associated with an identified pathogen or other laboratory parameters indicative of infection. Demographic information, prior illness and training history did not distinguish between presentations with or without objective measures of infection. Elevated white blood cell and neutrophil counts and lower Vitamin D concentrations partially distinguished infectious episodes. At the time of presentation to the clinic, the number of systemic symptoms/behaviors (cough, headache, earache, fatigue, fever/rigors, myalgia/arthralgia, or cessation of training prior to clinic attendance) had some predictive value for infection: odds ratio per symptom 1.23 (90% confidence interval: 0.91-1.66); probability of infection 48% with no symptoms to 77% with six symptoms. Laboratory investigation also identified allergy in a considerable proportion of the cohort (39%).

Conclusions
In the current study, a discrepancy was noted between physician and laboratory diagnosed infection in elite athletes. This discrepancy highlights the need for consideration of alternate diagnostic options when evaluating upper respiratory symptoms in athletes. A considerable proportion of episodes of respiratory symptoms in athletes were not associated with identification of a respiratory pathogen. Other potentially treatable causes of upper respiratory symptoms therefore warrant consideration in athletic populations, particularly in athletes with recurrent symptoms.

The full manuscript of this study can be found in: Clinical Journal of Sport Medicine. 2008;18:438-445.