Sensitivity of Raman spectroscopy to normal patient variability

Abstract

Many groups have used Raman spectroscopy for diagnosing cervical dysplasia; however, there have been few studies looking at the effect of normal physiological variations on Raman spectra. We assess four patient variables that may affect normal Raman spectra: Race/ethnicity, body mass index (BMI), parity, and socioeconomic status. Raman spectra were acquired from a diverse population of 75 patients undergoing routine screening for cervical dysplasia. Classification of Raman spectra from patients with a normal cervix is performed using sparse multinomial logistic regression (SMLR) to determine if any of these variables has a significant effect. Results suggest that BMI and parity have the greatest impact, whereas race/ethnicity and socioeconomic status have a limited effect. Incorporating BMI and obstetric history into classification algorithms may increase sensitivity and specificity rates of disease classification using Raman spectroscopy. Studies are underway to assess the effect of these variables on disease.

Figure 1

(a) Normalized average Raman spectra of white, black, and Hispanic patients. Highlighted regions are displayed in (c–e). (b) Difference spectra between measurements from white and black patients and white and Hispanic patients. (c–e) Box plots of specific peaks of Raman spectra from normal cervix of patients who described themselves as white, black, or Hispanic. Potential peak assignments: (c) Lipid and DNA, (d) phenylalanine and DNA, (e) Amide I shoulder. The box contains data between the 25th and 75th percentile, with the centerline representing the median. The error bars are ±1 S.D. about the mean. Outliers are represented by +.

Figure 2

(a) Normalized average Raman spectra from normal, overweight and obese patients. Highlighted regions are displayed in (c–e). (b) Difference spectra between measurements from normal and overweight patients and normal and obese patients. (c–e) Box plots showing regions of difference between patients with normal and overweight + obese BMI levels. Potential peak assignments: (c) phenylalanine, (d) lipid, (e) C = C bond. The box contains data between the 25th and 75th percentile, with the centerline representing the median. The error bars are ±1 S.D. about the mean. Outliers are represented by +.

Figure 3

(a) Normalized average Raman spectra from patients with zero pregnancies and one or more pregnancy. Highlighted regions are displayed in (c–e). (b) Difference spectra between measurements from patients with and without previous pregnancy. (c–e) Box plots showing regions of difference between patients with and without previous pregnancy. Potential peak assignments: (c) collagen/elastin, (d) Amide III, (e) C–O stretch. The box contains data between the 25th and 75th percentile, with the centerline representing the median. The error bars are ±1 S.D. about the mean. Outliers are represented by +.

Figure 4

(a) Normalized average Raman spectra from patients with and without health insurance. Highlighted regions are shown in (c–e). (b) Difference spectra between measurements from patients with and without health insurance. (c–e) Box plots showing regions of difference between patients with and without health insurance. Potential peak assignments: (c) ${\mathrm{PO}}_2^{-1}$, (d) protein content, (e) Amide I shoulder. The box contains data between the 25th and 75th percentile, with the centerline representing the median. The error bars are ±1 S.D. about the mean. Outliers are represented by +.