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Diagnostic tools are usually descriptive and enable diseases to be categorized. They tend to be qualitative rather than quantitative thereby limiting their use for epidemiological surveys. However, for computation purposes, they have weighted scores which enables analysis of data.

Such diagnostic tools include observational and behavioural rating scales. These are the most frequently used measures for diagnosing dental fear in children17. It is easy to administer, non-intrusive when in use and easy to conceptualise18. The rates use exhibited traits as an organizing concept to select relevant cues which is used to aid the superimposition of a dimension to the subject?s behaviour18.

Various rating scales for measuring behaviours have been developed over the years. One of these is the Frankl scale developed by Frankl et al19. It rates children?s reaction to dental treatment on a scale. The scale consists of four categories of behaviour, ranging form definitely negative to definitely positive. It has been used in a number of epidemiological studies.

Another scale is the Melamed Behaviour Profile Rating Scale20. It consists of 27 child related behaviour indicative of dental fear. These factors are weighted by a number that reflects the degree of its disruptiveness. The total score is obtained by multiplying the frequency at which behaviour in each category occurs by its weighted number. Each child is assessed every three minutes. The weighted frequencies are then added across categories and the sum is divided by the number of 3 minutes intervals observed. It has been demonstrated to be reliable21 though its validity is not completely convincing22.

These behaviour ratings scales are often reported to have very high reliabilities19, 20,23-25. However, reports of low or weak correlations between the behaviour ratings and other measures exist16, 26-29 making the validation of these instruments problematic.

Behavioural rating scales measure situational fear. They are however subjective modalities for measuring dental fear, as there is the possible element of observer bias. A child?s behaviour in one situation might obviously influence the ratings made in other instances30. The dentist?s own personal opinions and views could also affect scoring30. These bias arise because scorer weighs the evidence in which the rating is based in a complex manner which is not easily specified or standardized18. Furthermore a clinical diagnosis of dental fear may be difficult to make in children who have developed coping mechanisms. Although these coping strategies lead to less clinical manifestation of dental fear31, they often enable the patient to tolerate the associated discomfort they perceive rather than be completely free from the fear. This allows for some element of bias in this subjective assessment as the assessor often equates a child?s dental fear with the ability to accept treatment. Moreover, obstinate behaviours and non-cooperation are not always due to dental fear. They could arise from a number of other reasons such as a spoilt child throwing temper tantrum in the clinic.