Equipercentile linking of the BPRS and the PANSS

The Positive and Negative Syndrome Scale (PANSS) and the Brief Psychiatric Rating Scale (BPRS) are the most frequently used scales to rate the symptoms of schizophrenia. There are many situations in which it is important to know what a given total score or a percent reduction from baseline score of one scale means in terms of the other scale. We used the equipercentile linking method to identify corresponding scores of simultaneous BPRS and PANSS ratings in 3767 patients from antipsychotic drug trials. Data were collected at baseline and at weeks 1, 2, 4 and 6. BPRS total scores of 18, 30, 40 and 50 roughly corresponded to PANSS total scores of 31, 55, 73 and 90, respectively. An absolute BPRS improvement of 10, 20, 30, 40 points corresponded to a PANSS improvement of 15, 32, 50, and 67. A percentage improvement of the BPRS total score from baseline of 19%, 30%, 40% and 50% roughly corresponded to percentage PANSS improvement of 16%, 25%, 35%, and 44%. Thus a given PANSS percent improvement was always lower than the corresponding BPRS percent improvement, on the average by 4-5%. A reason may be the higher number of items used in the PANSS. These results are important for the comparison of trials that used these rating scales. We present a detailed conversion table in an online supplement.