Improving the Diagnosis of Invasive Fungal Infections in Critically Ill Patients.

Invasive fungal infection is a major success-limiting factor in modern healthcare, especially for the immunocompromised and those in the critical care unit setting. Yeasts such as Candida albicans and Candida glabrata are implicated in deep-seated infections - including bloodstream infections - in Critical Care Unit patients, and the mould Aspergillus fumigatus in the immunocompromised such as solid organ and stem cell transplant recipients.

Although yeasts are often recovered from blood cultures, generally fungal infection – and aspergillosis in particular - goes undiagnosed or diagnosis is delayed as cultures are persistently negative.

A delay in diagnostics worsens prognosis. Critically ill patients may receive expensive antifungal drugs empirically to provide cover for these infections, and these drugs are not without side-effects.

 Figure 1: Aspergillus Fumigatus. Courtesy of Dr S. Braham 

To improve the diagnosis of invasive fungal infections in critically ill patients, Viapath offers a test for Beta-D-glucan (BDG). BDG is a cell wall molecule produced by both yeasts and filamentous fungi, such as Aspergillus spp. Effectively, it is a ‘pan-fungal marker’ the presence of which indicates invasive fungal infection, be it yeast or mould. Thus BDG can be used to monitor patients, both those on treatment and those at risk of infection.

BDG is found at very low concentrations in the blood of healthy individuals (10-40 pg/mL) but at concentrations exceeding 80 pg/mL in established fungal infection. The assay has a high negative predictive value: a negative BDG result encourages reconsideration of the need for antifungal therapy in patients receiving such agents.

 Figure 2: BDG Assay plate. Courtesy of Dr S. Braham

Viapath’s Infection Science Department at King’s College Hospital, now uses the CE marked Fungitell assay which is a rapid colorimetric assay for the detection of BDG in the serum of patients with symptoms of, or medical conditions predisposing to, invasive fungal infection.

For patients at prolonged risk of developing invasive fungal infections, samples may be tested twice weekly as a “screening” test. Specimens may also be submitted from patients, in critical care units, with a prolonged pyrexia which is unresponsive to antibacterials and therefore suspected of having a fungal infection. A sample of clotted serum is required for the test and the turnaround time is 36-48 hours.

For further information on Viapath’s BDG test contact

Dr Sharleen Braham 020 3299 2571 or at SBraham [at] nhs [dot] net

For further information on the clinical aspects of BDG testing, please contact:

Dr Jim Wade: Jimwade [at] nhs [dot] net

Dr Anita Verma: Anitaverma [at] nhs [dot] net