title: Premenstrual syndrome: comparison between different methods to diagnose cyclicity using daily symptom ratings.
abstract: BACKGROUND
  In the diagnosis of premenstrual syndrome (PMS) the technique of daily prospective symptom ratings is often used. Several methods of assessing cyclicity, based on the daily prospective symptom ratings, have been presented in the literature. In this paper we compare four different methods to assess cyclicity.
  
  
  METHODS
  Eighty consecutive patients seeking help for PMS at the Department of Gynecology completed daily symptom ratings using a visual analogue scale (VAS) during one menstrual cycle. They also made an Eysenck Personality Inventory (EPI) and a thorough case history was taken regarding earlier psychiatric case history. The methods compared were: a) the nonparametric Mann-Whitney U-test, b) effect size, c) Run-test and d) a 30% change in symptom degree between the follicular and the luteal phase calculated in two different ways.
  
  
  RESULTS
  There was good agreement in the number of cyclic and non-cyclic patients between the different diagnostic methods used with exception of the 30% of change methods as the criteria for cyclicity. Here the number of non-cyclic patients became higher and lower, respectively, than with the other methods. The correlation between the number of symptoms for each patient showing cyclicity was high in all tests. When comparing the median neuroticism score of the EPI-N inventory the non-parametric, the Run-test and the effect size showed significant differences between the non-cyclic group and the group of patients with pure PMS, but not the 30%-change methods. Frequency of patients with psychiatric history showed similar results.
  
  
  CONCLUSIONS
  Three of the methods used seem to identify the same patients as having or not having cyclical changes and probably also then finding the same biological and/or psychological factor being responsible for the cyclicity. There were, however, some differences in outcome of validity testing and the 30%-change methods seem less valid than the other three methods. Due to its simplicity and theoretical/statistical advances the Run-test seems most preferable.
authors.affiliation: Department of Physiology, University of Umeå, Norrlands University Hospital, Sweden.
authors.forename: U B
authors.initials: UB
authors.lastname: Ekholm
authors.forename: N O
authors.initials: NO
authors.lastname: Ekholm
authors.forename: T
authors.initials: T
authors.lastname: Bäckström
mesh_terms: D000328:Adult; D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D008722:Methods; D008875:Middle Aged; D010507:Periodicity; D010555:Personality Inventory; D011293:Premenstrual Syndrome / Q000175:diagnosis* / Q000503:physiopathology / Q000523:psychology; D015203:Reproducibility of Results; D012647:Self-Assessment; D018709:Statistics, Nonparametric