The Roth score as a triage tool for detecting hypoxaemia in general practice: a diagnostic validation study in patients with possible COVID-19

Validity of the "Roth score" for hypoxemia screening

INTRODUCTION

The Roth score is an alternative strategy to estimate oxygen saturation by using a simple verbal test. We designed this clinical study to assess the validity of the Roth score (Spanish version) as a screening test for hypoxemia. A secondary objective was to evaluate the agreement and consistency between the oxygen saturation obtained via pulse oximetry (SpO₂) and arterial blood gas test (SaO₂).

METHODS

An observational study was conducted in two hospital emergency departments. Adult patients who underwent arterial blood gas tests were included in the analysis. Pulse oximetry values were determined, and the Roth score was applied in the Spanish language. The validity of the Roth score was assessed in terms of sensitivity and specificity by creating ROC curves and by calculating the area under the curve (AUC) for SpO₂, SaO₂, and oxygen pressure in the arterial blood (PaO₂). Agreement between SpO₂ and SaO₂ values was assessed by using the intraclass correlation coefficient (ICC), and consistency between both measures was calculated by following the method of Bland and Altman.

RESULTS

The ROC curve models of the Roth score results that were obtained for SaO₂ < 90%, ≤92%, and < 95% had AUCs of 0.574, 0.462, and 0.543, respectively, for the highest number that was obtained in the test, as well as AUCs of 0.403, 0.376, and 0.495, respectively, for the maximum time that was used. The AUCs for PaO₂ ≤ 60, ≤70, and ≤80 mmHg were 0.534, 0.568, and 0.512, respectively, for the maximum number that was obtained in the test, as well as AUCs of 0.521, 0.515, and 0.519, respectively, for the maximum time that was spent. The ICC between SaO₂ and SpO₂ was 0.817 (p < 0.001); additionally, the mean difference between the two measurements was -0.55.

CONCLUSION

The Roth score performed in Spanish is not a valid test for hypoxemia screening. There is sufficient agreement and consistency between SaO₂ and SpO₂ measurements.

Hypoxemie detecteren met de Roth-score

In de COVID-19-pandemie werd beoordeling op afstand belangrijk, maar het kan lastig zijn om op afstand de respiratoire status van de patiënt in te schatten. Een eenvoudig hulpmiddel is de Roth-test: instrueer de patiënt om in 1 uitademing zo snel mogelijk tot 30 te tellen en noteer tot welk getal deze komt (counting number) en hoeveel seconden dat kost (counting time). We lieten 33 huisartsen de Roth-test uitvoeren bij 105 patiënten en vonden dat een counting number ≥ 20 samenhangt met een verlaagde SpO2 (sensitiviteit 93,3%, specificiteit 77,8%). Uitgebreider validatieonderzoek is echter nodig om de test te kunnen implementeren in triageprotocollen.