Clinical Validation of Vital-PICASO for Predicting Hypotension Within 24 Hours in General Ward Inpatients

This study was a retrospective, single-center, superiority-confirmatory clinical performance study conducted at Seoul National University Hospital.

Data Source and Study Population

Electronic medical records were reviewed for patients aged 19 years or older who had been admitted to a general ward for at least 12 hours between January 1, 2023, and May 31, 2025. Clinical data previously used in the development of Vital-PICASO were excluded.

The collected variables included systolic blood pressure, diastolic blood pressure, heart rate, respiratory rate, body temperature, oxygen saturation when available, and the corresponding measurement times. Additional variables included the occurrence, time, and location of hypotension; month and year of birth; sex; height and weight when available; do-not-resuscitate status; pregnancy status; date of admission to the general ward; clinical department; and the vital-sign data collection period.

Data Selection

Potentially eligible hypotension-positive and hypotension-negative data were identified from the electronic medical record system. To reduce selection bias, candidate data were numbered and randomly selected by an independent statistician using R or SAS software.

Hypotension-positive data were defined as data from patients who experienced hypotension, defined as systolic blood pressure below 90 mmHg, in a general ward. Vital-sign data from up to 72 hours before the first eligible hypotension event were collected. If hypotension occurred within 24 hours after admission or transfer to the general ward, all available vital-sign data recorded before the event were collected, provided that at least 12 hours of data were available.

Hypotension-negative data were obtained from patients who did not experience hypotension during the selected general ward admission. Negative data were randomly selected from the same wards and from time intervals comparable with those of the positive cases. Vital-sign data from up to 72 hours after general ward admission or around the selected reference time point were collected. Only one eligible data interval was selected per patient.

The final study dataset consisted of 648 data cases, including 324 hypotension-positive cases and 324 hypotension-negative cases. Two analysis datasets were evaluated: 168 cases for the analysis including oxygen saturation, consisting of 84 positive and 84 negative cases, and 480 cases for the analysis excluding oxygen saturation, consisting of 240 positive and 240 negative cases. Data cases could be used in both analysis datasets.

Reference Standard Establishment

The initial hypotension-positive or hypotension-negative classification was determined according to the predefined systolic blood pressure criterion. To improve the reliability of the study dataset, a clinician with at least 1 year of clinical experience independently reviewed the data collection reference time point and relevant patient information while blinded to the initial positive or negative classification. The clinician's final classification was used as the reference standard.

Application of the Investigational Device

The medical device operator received vital-sign datasets identified only by screening numbers and was blinded to the reference-standard classification. Each dataset was analyzed using Vital-PICASO to estimate the risk of hypotension within 24 hours. The peak risk score and corresponding time within the analysis interval were recorded.

Statistical Analysis

The software-generated risk scores were compared with the reference-standard classifications. The primary performance measures were the area under the receiver operating characteristic curve for:

• the model including oxygen saturation; and
• the model excluding oxygen saturation.

The AUROC for each model was compared with the prespecified comparator performance value of 0.7847. The performance criterion for each primary outcome was met if the lower bound of the 95% confidence interval for the difference between the Vital-PICASO AUROC and the comparator AUROC was greater than zero. The overall study was considered successful if both primary outcomes met their respective performance criteria.

Secondary performance measures included comparison with the predictive performance of the National Early Warning Score and Modified Early Warning Score, area under the precision-recall curve, precision, recall, F1 score, threshold-specific performance, performance by prediction-time interval, and cumulative-time performance.

Because the study used previously collected electronic medical record data, there was no direct participant contact, additional examination, treatment, or change in clinical care.

Inclusion criteria

General Criteria

• Male or female patient aged 19 years or older at the time the clinical data were recorded
• Electronic medical record data available between January 1, 2023, and May 31, 2025
• Admission to a general ward for at least 12 hours
• Clinical data not previously used in the development of Vital-PICASO

Hypotension-Positive Group

• Hypotension occurred in a general ward
• Hypotension was defined as systolic blood pressure below 90 mmHg
• Vital-sign data were available for up to 72 hours before the hypotension event
• If hypotension occurred within 24 hours after admission or transfer to the general ward, all available vital-sign data recorded before the event were included
• If a patient experienced multiple hypotension events during the data collection period, only the first eligible event was included

Hypotension-Negative Group

• No hypotension occurred during the selected general ward admission period
• Data were randomly selected from the same general wards as the hypotension-positive group
• Vital-sign data were available from a time interval comparable with the hypotension event reference time or for up to 72 hours after admission to the general ward
• Only one eligible data interval was included per patient
• The data were considered appropriate for inclusion in the hypotension-negative group by the investigator

Exclusion criteria

• Hypotension occurred outside a general ward
• A do-not-resuscitate order was in effect at the time of data collection
• Pregnancy at the time of data collection or within 3 months after delivery
• The data were considered inappropriate for the study by the principal investigator