Population seeking help at CHR services | |||
---|---|---|---|

Psychotic disorder as defined with the gold standard ICD/DSM | |||

Developing psychosis | Not developing psychosis | ||

CHR assessment outcome | At Risk (CHR+) | CHR+ T (true positive) | CHR+ NT (false positive, type I error) |

Not At Risk (CHR−) | CHR− T (false negative, type II error) | CHR− NT (true negative) | |

Pretest probability (x-axis in figure 2) | The probability of developing psychosis before the CHR assessment, also called the prevalence of the disease: (true positive+false negative)/(true positive+false postive+false negative+true negative) | ||

Sensitivity | Proportion of patients who will develop the psychosis who will have a positive CHR assessment result: true positive/(true positive+false negative} | ||

Specificity | The proportion of patients without the development of psychosis who will have a negative CHR assessment result: true negative/(true negative+false positive) | ||

Positive Predictive Value (PPV) | The proportion of patients with a positive CHR assessment result who actually have developed psychosis: true positive/(true positive+false positive) | ||

Negative predictive value (NPV) | The proportion of patients with a negative CHR assessment result who do not have actually developed psychosis: true negative/(true negative+false negative) | ||

Accuracy | The proportion of true results among the total number of CHR patients assessed: (true positive+true negative)/(true positive+false positive+true negative+false negative) | ||

Positive likelihood ratio LR+ (legend to figure 2) | The probability of a CHR patient who develop psychosis testing positive at the CHR assessment divided by the probability of a person who does not develop the psychosis testing positive at the CHR assessment: sensitivity/(1-specificity) | ||

Negative likelihood ratio LR− (legend to figure 2) | The probability of a patient who develop psychosis testing negative at the CHR assessment divided by the probability of a patient who does not develop psychosis testing negative at the CHR assessment: (1-sensitivity)/specificity | ||

Post-test positive probability (red line in figure 2) | The individual probability of developing the disease given a positive prognostic test result: Pretest probability×Sensitivity/((Pretest probability×Sensitivity)+(1−Pretest probability)×(1−Specificity)) | ||

Post-test negative probability (green line in figure 2) | The individual probability of developing the disease given a negative prognostic test result: (1−Pretest probability)×Specificity/((1−Pretest probability)×Specificity)+Pretest probability×(1−Sensitivity)) |

APS, attenuated psychosis symptoms; BIPS, brief intermittent psychotic symptoms; BLIPS, brief limited intermittent psychotic symptoms; BS, basic symptoms. Adapted from;8 CHR, clinical high risk (UHR and/or BS); DSM, Diagnostic and Statistical Manual; GRFD, genetic risk and deterioration syndrome; ICD, International Classification of Diseases; UHR, ultra high risk (including BLIPS/BIPS and/or APS and/or GRFD).