Title:
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Volatile organic compounds: novel potential
biomarkers in bladder cancer diagnosis
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Bladder cancer is an important global disease. The gold
standard for diagnosis is cystoscopy and biopsy; both are invasive and
require highly trained personnel. In a majority of cases, treated patients are
followed up by frequent cystoscopies lasting several years. The discovery of
biomarkers indicating which individuals should proceed to cystoscopy would
be an important addition to bladder cancer management.
The odour of urine is produced by volatile organic compounds, (VOCs),
detectable by gas chromatography and mass spectrometry (GC-MS). An
analysis of the VOCs in urine from various groups of individuals including
patients with bladder cancer is undertaken in search of possible discriminating
compounds, which could be harnessed in future as a potential screening tool
or adjunct in bladder cancer management.
Methods
First void urine was obtained from 64 patients with new non-muscle
invasive bladder cancer, 71 cancer free patients with haematuria and
51 asymptomatic volunteers. After equilibration, the headspace above these
pH adjusted urine samples was extracted for 20minutes, using a carboxen /
polydimethylsiloxane solid phase micro-extraction fibre (SPME). This was
followed by desorption and VOC identification by GC-MS.
Results
Urine headspace VOCs under acidic conditions, (pH of
modified urine 2), were found to be discriminating. Identified compounds
were analyzed using forward stepwise discriminant analysis: 9 VOCs when
used together, gave 84.7% correct classification of samples (Haematuria
control v Bladder cancer) with no change on cross validation of results. The
calculated sensitivity and specificity of this model is 76.6% and 92.9%
respectively, with Positive predictive value of 90.7% and Negative predictive
value of 92.9%. These results are comparable, and in some cases better than
those obtained using commercially available urinary bladder cancer
biomarkers.
Conclusion
Volatile organic compounds in urinary head space change with the development of bladder cancer. Urinary VOCs are exciting novel potential
biomarkers in the detection of bladder cancer.
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