Friday, 24 May 2013

Use of Aspergillus Galactomannan and PCR to Direct Treatment

Patients undergoing transplant as part of their therapy for leukemia are often at high risk of getting invasive aspergillosis (IA). Once IA is detected these patients are given antifungal drugs to protect them from infection but these drugs are expensive and can be quite toxic and difficult for the patient to tolerate so their use is kept to a minimum.
Traditionally IA in these cases is detected using a combination of culturing samples and searching for infection via miscroscope (histology). The former needs several days before it can be used to accurately identify an infecting fungus, days during which the infection gradually becomes harder to treat. There is an urgent need for more rapid and accurate diagnostic techniques to be used in these cases.

There are two tests that can give rapid results - direct detection of fungal fragments in the blood (galactomannans) and amplification of specific DNA sequences in blood samples (PCR)- both are not dependent on the immune system of the patient and are useful for cases such as these when the patients has had their immune system largely removed! Both are highly specific for the detection of fungal infection.

This study compares these two diagnostic strategies in a randomised controlled trial - one group being tested with culture & histology and the other with galactomannan & PCR. There were 120 or more patients in each group so this is a reasonable-sized study and its results are consequently more reliable.

Excitingly the use of the newer techniques led to a significant drop in the use of antifungal drugs in these patients with no drop in protection from IA. This result opens the way to detect IA more rapidly and more accurately and thus to direct the use of drugs more efficiently and effectively - this is a great step forward in the treatment of these patients.

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