Predicting the composition of gallstones by infrared spectroscopy.

Aim: To determine the composition of gallstones in South India by comparing visual assessment with graphic interpretation of infrared spectra.
Methods: Infrared spectroscopy (IRS) was used in qualitative analysis of 168 gallstones from Tamilnadu, Kerala and Karnataka and compared with visual interpretation. The spectrum of cholesterol, calcium bilirubinate and calcium carbonate for each stone was correlated with visual inspection.
Results: Fifty four percent of gallstones were of pigment variety, 43% were of mixed and the remaining 3% were cholesterol gallstones as categorised by visual interpretation. Based on infrared spectrocopic interpretation the percentages were 58%, 39% and 2% respectively. There was a good agreement between the visual inspection and IRS in classification of gallstones (Kappa value 85%; 95% CI 77-93%).
Conclusion: Visual inspection of gallstones can predict the composition of gallstone with good accuracy and was comparable to infrared spectroscopic interpretation.