The demographic profile of study subjects shows that the majority were between 30-64 years of age (70%), female (59%), non-white race (54%), and were not college graduates (54%) (). Demographically, 31% were foreign born and 22% were Latino. Also, 22% scored positive on the PCPS (i.e., they had 3 positive PTSD symptoms) at baseline and 47% had at least one positive lifetime depression symptom on the PHQ-2 scale. Furthermore, 20% had high exposure (i.e., 4+ events) to lifetime traumatic events, 32% reported difficultly sleeping in the past year, and 11% did not have regular access to healthcare. Twenty-two percent (22%) had experienced 2 or more negative life events in the past year and 18% were non-right-handed. Furthermore, 46% reported moderate to severe pain impairment in the past 4 weeks and 30% scored low in self-esteem. All these predictor variables were measured at the initial (baseline) assessment and were significant in prospectively predicting PTSD in the follow-up period. The prevalence of PTSD at follow-up was 8% ().
The results for predicting PTSD prospectively from baseline predictors are shown in . As suggested, the PCPS was selected because of its wide clinical use, previous research, and because these screener symptoms were also included in the PTSD symptoms scales used in previous trauma studies. As can be seen, the primary care PTSD screener alone has a sensitivity of 60.5% and a specificity of 80.9% in predicting PTSD at 12-month follow-up, resulting in an area under the receiver operating curve (AUC) = 0.707 (95% CI = 0.664-0.750). Adding the predictors from the original NY PTSD Risk Score, including sleep disturbance, depression symptoms, trauma exposure, and access to healthcare, resulted in a sensitivity of 76.9% and a specificity of 69.4%, with an AUC = 0.774 (95% CI = 0.730-0.810). This resulted in a significant improvement in the prediction model over the base model with only the PCPS (p < 0.0001). Adding the four additional longitudinal risk factors identified, including negative life events in the past year, baseline pain status, baseline self-esteem, and reported handedness, resulted in a sensitivity of 67.2% and a specificity of 82.7%, with an AUC = 0.819 (95% CI = 0.781-0.856). This also resulted in a significant improvement over the previous model that included the PCPS and the original NY Risk Score factors (p = 0.001). Finally, adding demographic factors, in this case Latino ethnicity and birth status, resulted in a sensitivity of 87.3% and a specificity of 65.3%, with an AUC = 0.839 (95% CI = 0.804-0.873), also a significant improvement over the previous model with the PCPS and the original NY Risk Score plus additional predictor variables (p = 0.007).
Prediction Results using Different PTSD Models (N = 1681)*
Because the prevalence of PTSD at follow-up was relatively low (8%), the predictive value of a positive test (PV+) was generally less than 25%, while the predictive value of a negative test (PV-) was typically 96% to 98% (see ). However, we note that given our prediction model, if our study populations had a PTSD prevalence of ~20%, statistical simulations (using Pepi, version 4) suggested that the positive predictive value of a positive test would be generally 80% to 90%, a substantial improvement.
presents PTSD risk-score results (i.e., the final regression-derived weights) used to generate the classification results shown in . As seen, a positive score on the PCPS (i.e., 3 or more positive items) is given a base score of 100 (otherwise = 0) and the psychosocial, demographic, and additional measures are also given weights (or scores) relative to this score. This scoring is based on using logistic regression analyses, whereby the b coefficients in each of the logistic regression models predicting PTSD are converted to standardized weights using a nomogram, as noted. These weights are then used to calculate a PTSD risk score. The last row of shows the total cut-off score for a PTSD classification at follow-up, based on these risk-score weights: 100 for the PCPS used alone; 110 for the PCPS + NY Risk Score factors; 224 for the PCPS + NY Risk Score factors + additional risk factors; 182 for the PCPS + NY Risk Score factors + additional risk factors + demographic factors.
Modified NY PTSD Risk Score Weights for Primary Care PTSD Screener (PCPS), Original NY Risk Score Factors, Additional Longitudinal Factors and Demographic Factors