A 5-category Obstetric Triage Acuity Scale (OTAS) was developed with a comprehensive set of obstetrical determinants. The objectives of this study were as follows: (1) to test the interrater reliability of OTAS and (2) to determine the distribution of patient acuity and flow by OTAS level. To test the interrater reliability, 110 triage charts were used to generate vignettes and the consistency of the OTAS level assigned by 8 triage nurses was measured. OTAS performed with substantial (Kappa, 0.61 – 0.77, OTAS 1-4) and near perfect correlation (0.87, OTAS 5). To assess patient flow, the times to primary and secondary health care provider assessments and lengths of stay stratified by acuity were abstracted from the patient management system. Two-thirds of triage visits were low acuity (OTAS 4, 5). There was a decrease in length of stay (median [interquartile range], minutes) as acuity decreased from OTAS 1 (120.0 [156.0] minutes) to OTAS 3 (75.0 [120.8]). The major contributor to length of stay was time to secondary health care provider assessment and this did not change with acuity. The percentage of patients admitted to the antenatal or birthing unit decreased from 80% (OTAS 1) to 12% (OTAS 5). OTAS provides a reliable assessment of acuity and its implementation has allowed for triaging of obstetric patients based on acuity, and a more in-depth assessment of the patient flow. By standardizing assessment, OTAS allows for opportunities to improve performance and make comparisons of patient care and flow across organizations.
Most emergency departments in North America use triage tools to ensure that patients requiring acute care receive priority treatment and to determine which patients can safely wait. The Canadian Triage and Acuity Scale (CTAS) was introduced in 1999 and revised in 2006 and 2008. It has been studied extensively and has high degrees of both reliability and validity. However, CTAS includes only a small number of high acuity obstetric determinants that do not reflect the diversity of patients assessed in an obstetric triage unit.
Obstetric triage units face many of the same challenges that led to the development and implementation of triage scales in emergency departments. The need to address access to care and long wait times, to assess acuity and workloads, and to increase accountability for limited resources led the Canadian Association of Emergency Physicians to develop a clear system that triages patients consistently within an institution and allows for comparison between institutions. The ability to triage, evaluate, and treat patients has been shown to reduce length of stay and increase patient satisfaction scores.
At London Health Sciences Centre (LHSC), obstetric triage provides 24 hour a day urgent and emergent care for all pregnant women beyond 20 weeks’ gestation from the London area and for tertiary referrals from the southwest region of Ontario. Before restructuring of the London hospitals, obstetric triage services were provided at 2 sites. In June 2011, all obstetric services in London were amalgamated at LHSC and approximately 11,300 patients were seen in the new obstetric triage unit in the first year. In planning for this amalgamation, we sought to better understand the volume and acuity in triage and to look for opportunities to improve the quality of care and patient flow. To facilitate this, the perinatal program at LHSC developed and implemented a 5-level acuity classification scale that reflected the variety of patients seen in the obstetric triage unit. The purposes of this study were to (1) measure the interrater reliability and validity of the Obstetric Triage Acuity Scale (OTAS) and (2) assess the distribution of acuity and patient flow by OTAS level.
Materials and methods
This study (17702E) was approved by the Western University Research Ethics Board on Feb. 10, 2011.
Interrater reliability
OTAS was modeled on the 5-category (1-Resusitative, 2-Emergent, 3-Urgent, 4-Less Urgent, 5-Nonurgent) CTAS tool. The acuity color coding and goals for time to assessment were replicated. A comprehensive set of obstetric modifiers was developed to reflect the variety of presentations and indications for referral to obstetric triage ( Figure 1 ). An expert review panel comprised of physicians and nurses reviewed the classification system for accuracy and completeness of obstetric modifiers.
To assess the interrater reliability (IRR), an educational program was provided to all the triage nurses. Eight nurses were randomly selected and assigned triage levels to clinical scenarios based on actual patient visits. These scenarios were from randomly selected 4 hour time blocks (2 per day) from June 1, 2011, to Jan. 31, 2012. The short vignettes containing the initial set of facts presented to a triage nurse were incorporated into an online questionnaire using Survey Monkey. We measured interrater agreement using the weighted Kappa to account for multiple raters, multiple categories, and for similar classification by chance alone. The calculated sample size of 110 scenarios was based on a Kappa correlation level of 0.8, a confidence interval of 95%, and 8 raters.
Validity
As an initial assessment of the validity of OTAS, admission to the birthing and antenatal units was determined from the chart review (Jan. 1, 2009 to Dec. 31, 2010) and used as a surrogate measure of resource use. The proportion of patients requiring admission was stratified by OTAS level to examine the relationship between the acuity level and hospital resource use.
Patient flow and acuity analysis
Before the 2011 merger, current state value stream maps of patient flow at St. Joseph’s Health Care Centre (SJHC) and LHSC were developed. The maps outlined every task performed during a triage visit including all resources used (physical space, human), as well as the length of time required at each step. Leveraging best practices in patient care, we created a future state Value Stream Map for the new obstetric triage unit. In planning for the new unit, we assessed the (1) volume, (2) length of stay (LOS), and (3) distribution of acuity at each site premerger and combined the data to create a citywide dataset.
First, to assess patient volumes, we performed a retrospective analysis (Jan. 1, 2009 to Dec. 31, 2010) using electronic data from our local patient registration and management systems. The patient volumes were analyzed by time of day and day of week.
Second, to assess LOS (as discharge time was not initially captured by our electronic system), the time to key tasks (initial nursing assessment, and secondary health care provider assessment [physician, resident or midwife]) and acuity, a paper chart review was performed on a representative sample of triage visits (Jan. 1, 2009 to Dec. 31, 2010) at both sites. Calculations of the sample sizes to capture a representative cohort (95% confidence level) and make inferences to the entire population given annual triage visit volumes were performed (LHSC–total visits 9829, sample size 566 visits, SJHC–total visits 12754, sample size 573 visits). Acuity was assigned based on the OTAS tool by 2 independent reviewers. The distribution of acuity was determined for both SJHC and LHSC before the merger based on OTAS level as percent of the total. The median times to registration, to primary nursing assessment, to secondary health care provider assessment and the LOS were stratified by acuity. Overall LOS and time to assessment were compared using the Kruskel–Wallis test and the Mann Whitney was used to compare times at each OTAS level.
A preliminary assessment of patient flow (volumes and LOS [June 1, 2011–Jan. 31, 2012]) and distribution by acuity (April 1–Aug. 31, 2012) was performed postmerger as data was available electronically. Compliance of acuity assignment by nursing staff was also assessed.
Results
Interrater reliability
IRR was calculated for each category using both direct correlation and the weighted Kappa correlation ( Table 1 ). Based on Kappa references outlined by Landis and Koch (<0 = poor, 0-0.20 = slight, 0.21-0.40 = fair, 0.41-0.60 = moderate, 0.61-0.80 = substantial, and 0.81-1.0 = almost perfect) overall the OTAS tool showed (Kappa – 0.71) “substantial reliability.” We found “near perfect” reliability for OTAS-5 and “substantial reliability” at the OTAS 1-4 levels.
| Measure | Weighted Kappa | Direct correlation coefficient |
|---|---|---|
| OTAS 1 | 0.7685 | 0.8750 |
| OTAS 2 | 0.7283 | 0.8382 |
| OTAS 3 | 0.6104 | 0.7500 |
| OTAS 4 | 0.6482 | 0.7532 |
| OTAS 5 | 0.8664 | 0.8347 |
| Overall | 0.7147 | 0.7898 |
Validity
The proportion of patients admitted to the antenatal or birthing unit was stratified by OTAS level ( Figure 2 ). Admission to the antenatal unit correlated well with acuity. Birthing unit admission correlated with acuity for OTAS 3 to 5. The greatest contributor to birthing room admission in OTAS 3 was term labor. The admission rates to the birthing unit for OTAS 1 and 2 were less than OTAS 3. The combined admission rate correlated better across all the OTAS levels.
Patient flow and acuity analysis
Figure 3 shows the triage volumes by time of day (combined LHSC and SJHC, Jan. 1, 2010–Dec. 31, 2010) over 1 year. The distribution of volume postmerger was similar with peaks at 1000 and 1900 hours, and two-thirds of the 24-hour volume presented between 0700 and 1900 hours.
There were some differences in the distribution of acuity ( Table 2 ) at the premerger sites (likely because SJHC was the tertiary care center premerger). The citywide premerger distributions for OTAS 1-3 match very closely to those captured electronically from postmerger. Combining OTAS 4 and 5 patients, 68% (premerger) and 67% (postmerger) of the patients seen were of lower acuity.
| Variable | LHSC 09-10 | SJHC 09-10 | Citywide 09-10 | LHSC Apr-Aug 2012 |
|---|---|---|---|---|
| OTAS 1 | 1% | 2% | 2% | 1% |
| OTAS 2 | 3% | 17% | 11% | 11% |
| OTAS 3 | 10% | 26% | 19% | 21% |
| OTAS 4 | 39% | 22% | 29% | 40% |
| OTAS 5 | 48% | 32% | 39% | 27% |
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