The following information relates to the psychometric properties of the PSC:
Instructions for Scoring: The PSC consists of 35-items that are rated as never, sometimes, or often present and scored 0, 1, and 2, respectively. Item scores are summed and the total score is recoded into a dichotomous variable indicating psychosocial impairment. For children aged six through sixteen, the cut-off score is 28 or higher. For four and five year-old children, the PSC cut-off is 24 or higher (Little et al, 1994; Pagano et al, 1996). Items that are left blank by parents are simply ignored (score = 0). If four or more items are left blank, the questionnaire is considered invalid.
How to Interpret the PSC: A positive score on the PSC suggests the need for further evaluation by a qualified health (M.D., R.N.) or mental health (Ph.D, LICSW) professional. Both false positives and false negatives occur, and only an experienced clinician should interpret a positive PSC score as anything other than a suggestion that further evaluation may be helpful. Data from past studies using the PSC indicate that 2 out of 3 children who screen positive on the PSC will be correctly identified as having moderate to serious impairment in psychosocial functioning. The one child "incorrectly" identified usually has at least mild impairment, although a small percentage of children turn out to have very little actually wrong with them (e.g., an adequately functioning child of an overly anxious parent). Data on PSC-negative screens indicate 95% accuracy, which, although statistically adequate, still means that 1 out of 20 children rated as functioning adequately may actually be impaired. The inevitability of both false-positive and false-negative screens underscores the importance of experienced clinical judgment in interpreting PSC scores. Therefore, it is especially important for parents or other lay people who administer the form to consult with a licensed professional if their child receives a PSC-positive score.
Validity: Using a Receiver Operating Characteristic Curve, Jellinek, Murphy, Robinson, et al (1988) found that a PSC cutoff score of 28 has a specificity of 0.68 and a sensitivity of 0.95 when compared to clinicians’ ratings of children’s psychosocial dysfunction. In other words, 68% of the children identified as PSC-positive will also be identified as impaired by an experienced clinician, and, conversely, 95% of the children identified as PSC-negative will be identified as unimpaired.
Reliability: Test-re-test reliability of the PSC ranges from r = .84 - .91. Over time, case/not case classification ranges from 83% - 87%. (Jellinek & Murphy, 1988; Murphy et al, 1992).
Inter-item Analysis: Our studies (Murphy & Jellinek, 1985; Murphy, Ichinose, Hicks, et al, 1996) also indicate strong (Cronbach alpha = .91) internal consistency of the PSC items and highly significant (p < 0.0001) correlations between individual PSC items and positive PSC screening scores.
Qualifications for Use of the PSC: The training required may differ according to the ways in which the data are to be used. Professional school (e.g., medicine or nursing) or graduate training in psychology of at least the Master’s degree level would ordinarily be expected. However, no amount of prior training can substitute for professional maturity, a thorough knowledge of clinical research methodology, and supervised training in working with parents and children. There are no special qualifications for scoring.