Colorimetric Breath Test Detects Lung Cancer

By David S. MacDougall

Thorax

Cleveland Clinic researchers have developed a colorimetric sensor array capable of identifying the unique chemical signature of lung cancer in a person's breath (. 2007; 62:565-568).

The technique is associated with a moderate degree of accuracy and, with refinement, may provide the basis for an inexpensive, noninvasive screening or diagnostic test for lung cancer.

"There is a need for an accurate lung cancer screening test," said Peter Mazzone, MD. "This test may be useful for identifying lung cancer in people at risk and may also help triage patients with abnormal findings on chest imaging."

According to Dr Mazzone, metabolic changes within cancer cells maylead to alterations in the cellular production and processing of volatile organic compounds (VOCs). Patterns of VOCs unique to lung cancer have previously been identified in exhaled breath by using sophisticated techniques including gas chromatography and mass spectroscopy.

The colorimetric sensor array incorporates a group of 36 spots impregnated on a disposable cartridge (Figure, see print issue). The colors of the spots change based on the VOC to which they are exposed, and the color changes are detected in a colorimetric instrument and evaluated for patterns unique to lung cancer.

The performance of the system was determined in a study of 143 participants. The study group included49 patients with non?small-cell lung cancer, 18 with chronic obstructive pulmonary disease, 15 with idiopathic pulmonary fibrosis, 20 with pulmonary arterial hypertension, 20 with sarcoidosis, and 21 healthy controls.

Each study participant performedtidal breathing of unfiltered room air for 12 minutes while inhaling through their nose and exhaling through their mouth into a breath-collection device. The exhaled breath was drawn over a sensor array held in place on a flatbed scanner that was kept at body temperature.

The color-changing chemicals that make up the spots on the sensor array are sensitive to key VOCs present in the breath of patients with lung cancer.

Validation of the colorimetric sensor array revealed a sensitivity of 73.3% and a specificity of 72.4% for the diagnosis of lung cancer (P = .001). The performance of the device was not influenced by gender, age, smoking history, histology, tumor size, or cancer stage.

This essay can "detect the unique pattern of VOCs in the breath of patients with lung cancer with moderate accuracy," the authors write.

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"The accuracy of the assay needs to be improved to make it clinically useful," Dr Mazzone told . "This may require improved knowledge of the nature of the VOC differences, better breath collection and processing equipment, and advances in statistical analytic techniques."