Sir, we read with interest the recent paper by Bots et al. (BDJ 2014; 217: 80) on the assessment of oral dryness by photographic appearances of the tongue. Perhaps not surprisingly, visual inspection of photographs of tongues was unreliable in diagnosing oral dryness. We would concur with the authors conclusion that 'further clinical inspection of the oral cavity is indicated'.1

As mentioned by Dr Murray Thomson in his commentary, we have developed a scale for clinical oral dryness2 to try and address this exact problem. Most oral healthcare workers who see patients regularly can recognise a number of signs and symptoms which suggest that the patient may have a dry mouth, but assessment of the degree of dryness is notoriously difficult. It is apparent that a reproducible clinical scale of dryness might allow the clinician to determine whether the dryness is mild and could be managed with local measures and advice in the surgery (such as that secondary to xerogenic drugs) or whether it is severe and requires the patient to be referred for further investigation as to the cause and management. It is also important to distinguish between xerostomia which is accepted as reflecting symptoms of dryness and hyposalivation where a reduced salivary flow is demonstrated. Xerostomia is not always associated with hyposalivation3 which is why attempts to correlate the two are often unsuccessful.

A clinical oral dryness score (CODS) for clinical signs has been developed2 and has been found to be reliable and easy to use for routine assessment of the severity of dry mouth.4 The scale is based on ten key features of dry mouth, accompanied by example images, and allocates one point for each feature.2 The use of any single feature of dryness for assessment was found to be unreliable. CODS can be incorporated into the routine clinical assessment of dry mouth patients, particularly since the clinician would normally be undertaking most aspects of the clinical assessment routinely. In general practice, a low COD score (1-3) indicates mild dryness manageable normally in practice, whereas a high COD score (7-10) is an indication for referral for further investigation. CODS seems to be closely related to both the unstimulated salivary flow and the thickness of the mucin layer over the epithelium (mucosal wetness) suggesting a physiological basis to the feeling of xerostomia.3

Clinical diagnoses usually require both a clinical history and a clinical examination (often aided by investigations). Xerostomia and hyposalivation would appear to be no exception.