THE CLINICAL EVALUATION OF ANTIDANDRUFF SHAMPOOS 445 Nil 0 Very slight 1 Slight 2 Slight to moderate 3 Moderate 4 Severe 8 As in the case of the more detailed technique, it is vital to test the concordance between observers, examining the same subjects independently at the same time, as often as possible. Typical results of such concordance tests between a pair of examiners are shown in Table I. Whilst these are not as good as those obtained for the more detailed method and reported earlier (1) they nevertheless do show quite good agreement and indicate that a discrepancy of more than 'one place' is unusual. Even when concord- ance tests show good agreement between observers it is still considered advisable that each subject in a trial should always be examined by the same observer at successive inspections this will be specially important when some of the observers are relatively inexperienced. An observer is at no time allowed to see the subject's earlier records during an examination Table I Concordance between observers Assessment of dandruff: observer A Nil Very Slight Slight to Moderate Severe slight moderate Nil 21 6 Very slight 9 58 5 2 Slight 1 10 6 4 Slight to moderate 4 4 11 Moderate 1 1 4 15 -- Severe 5 Figures represent number of scalp quadrants and neither the observer nor the statistician know the breakdown of the product codes before the trial has been completed and analysed. Our earlier studies to investigate dandruff without particular reference to treatment, involved either weekly or fortnightly examination of subjects over long periods of time. Similarly in clinical trials using the same detailed procedure, we have made frequent inspections over long treatment periods

446 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS indeed, the less effective the treatment, the longer a trial needs to proceed in order to demonstrate a difference between test and control. However, with the records of earlier trials available for study and with more effective products now coming under test, it has been possible to show that the num- ber of inspections during a trial can be greatly reduced without detriment to the validity of the main findings, providing that the panel size is not too small. To make due allowance for any cumulative effect of a shampoo treatment it must be used several times before an attempt is made to measure its efficacy. Our experience suggests that a first examination before using the product should be followed by a second examination after four weeks' use and a third examination after eight weeks. Comparison of the third versus the first reading reveals the main trend, but the second exami- nation is a useful check on placebo effect which may be expected to be sub- stantially the same at the second and third examinations. When using this method we prefer to use panels at least twice the size of those used for the method with more frequent examinations. 22-- 20-- 18-- 14 [3 I[ o I 02 0 3 o4 2 4 6 8 I0 12 14 16 18 20 22 24 26 Dondruff index: de,oiled (30min) ,echnique Figure 3 Comparison between "5-minute" and detailed "30-minute" technique for dandruff inspection. Numbered points represent successive weekly averages for the same 10 subjects under treat- ment with (1-4) a non-medicated, and (5-15) an antidandruff shampoo. RESULTS Critical comparison of techniques for the assessment of dandruff ideally requires that the different methods should be used side-by-side on