## 5 Future Perspectives  
Vibrational spectroscopy shows great potential as a label free, high sensitivity and specificity test for cervical and oral cancer screening. The respective techniques of Raman and IR spectroscopy each has its own potential advantages for clinical applications (reviewed in [49]), with Raman spectroscopy having a higher spatial resolution, minimal sample preparation, and minimal interference from water and FTIR spectroscopy having a higher signal to noise ratio allowing faster acquisition times. ATR-FTIR spectroscopy can achieve higher spatial resolution and can allow measurement from aqueous samples. Recent advances in these techniques have included surface enhanced Raman spectroscopy (SERS), which allows significant enhancement of the Raman signal through close proximity/adsorption onto a roughened metal surface, a colloidal solution or a roughened electrode, tip enhanced Raman spectroscopy (TERS) which combines the high spatial resolution of atomic force microscopy with SERS, coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS) (reviewed in [50]) which allow rapid real time imaging of single cells, and the development of high brightness quantum cascade lasers to improve acquisition times for IR imaging. For cytology applications, a key consideration is that these spectroscopic techniques could fit into the current workflow. Both Raman and IR spectroscopy can be operated in microscopic mode and, with automated spectral acquisition, these techniques could be similar to the Thinprep Imager (Hologic) or the Focal Point GS Imaging system (BD), which use image processing algorithms to automatically review liquid based cytology Thinprep and SurePath slides. Both Raman and IR spectroscopy are reagent free, so costs should be favourable when compared to the imaging systems or to manual scoring where personnel costs could be reduced. A recent study [35] has shown that glass ThinPrep slides can be used for Raman spectral recording whereas spectroscopic substrates, such as MirrIR or calcium fluoride substrates, are used for IR spectroscopy and although they reduce the presence of confounding contributions of the substrate, they are considerably more expensive than the glass slides used in the cytology laboratory.  
However, much work still remains before these techniques could be translated into standard clinical practice [51]. Many studies have used relatively small sample sizes and as such may be biased. Screening populations are heavily weighted towards negative results with only a small percentage of positive results so validation in large multi centre studies is needed using real world cytology samples from screening populations. Large scale clinical trials are needed to obtain the large volumes of data necessary for the development of robust classification algorithms and histopathology rather than cytology should be used to classify the samples.  
If spectroscopy can be shown to be as good as, or better than, the gold standard histopathology, then there is great potential for these techniques to be used as an alternative or an adjunct to the current cytology screening methods. The advantages would be higher accuracy, higher throughput and reduced workload for the cytologist/pathologist and higher accuracy and chance of earlier detection for the patient.  
The authors acknowledge funding from Enterprise Ireland co-funded by the European Regional Development Fund (ERDF) and Ireland's EU Structural Funds Programme 2007-2013, CF2011 1045, Science Foundation Ireland, 12/IP/1494, and Dublin Institute of Technology Fiosraigh Research Excellence Award.  
[PERSON] conceived the idea for the manuscript and wrote the manuscript with input from [PERSON], [PERSON] and [PERSON].