Background During the COVID-19 pandemic, there have been concerns regarding potential bias in pulse oximetry measurements for people with high levels of skin pigmentation. We systematically reviewed the effects of skin pigmentation on the accuracy of oxygen saturation measurement by pulse oximetry (SpO2) compared with the gold standard SaO2 measured by CO-oximetry. Methods We searched Ovid MEDLINE, Ovid Embase, EBSCO CINAHL, ClinicalTrials.gov, and WHO International Clinical Trials Registry Platform (up to December 2021) for studies with SpO2–SaO2 comparisons and measuring the impact of skin pigmentation or ethnicity on pulse oximetry accuracy. We performed meta-analyses for mean bias (the primary outcome in this review) and its standard deviations (SDs) across studies included for each subgroup of skin pigmentation and ethnicity and used these pooled mean biases and SDs to calculate accuracy root-mean-square (Arms) and 95% limits of agreement. The review was registered with the Open Science Framework (https://osf.io/gm7ty). Results We included 32 studies (6505 participants): 15 measured skin pigmentation and 22 referred to ethnicity. Compared with standard SaO2 measurement, pulse oximetry probably overestimates oxygen saturation in people with the high level of skin pigmentation (pooled mean bias 1.11%; 95% confidence interval 0.29 to 1.93%) and people described as Black/African American (1.52%; 0.95 to 2.09%) (moderate- and low-certainty evidence). The bias of pulse oximetry measurements for people with other levels of skin pigmentation or those from other ethnic groups is either more uncertain or suggests no overestimation. Whilst the extent of mean bias is small or negligible for all subgroups evaluated, the associated imprecision is unacceptably large (pooled SDs > 1%). When the extent of measurement bias and precision is considered jointly, pulse oximetry measurements for all the subgroups appear acceptably accurate (with Arms < 4%). Conclusions Pulse oximetry may overestimate oxygen saturation in people with high levels of skin pigmentation and people whose ethnicity is reported as Black/African American, compared with SaO2. The extent of overestimation may be small in hospital settings but unknown in community settings. Review protocol registration https://osf.io/gm7ty

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Background Pulse oximetry was widely used in hospitals and at home to monitor blood oxygen during the COVID-19 pandemic. There have been concerns regarding potential bias in pulse oximetry measurements for people with dark skin. We aimed to assess the effects of skin pigmentation on the accuracy of oxygen saturation measurement by pulse oximetry (SpO2) compared with the gold standard SaO2 measured by CO-oximetry. Methods We searched Ovid MEDLINE, Ovid Embase, and EBSCO CINAHL Plus (up to December 2021), as well as ClinicalTrials.gov and World Health Organization International Clinical Trials Registry Platform (up to August 2021). We identified studies comparing SpO2 values in any population, in any care setting, using any type of pulse oximeter, with SaO2 by standard CO-oximetry; and measuring the impact of skin pigmentation or ethnicity on pulse oximetry accuracy. We performed meta-analyses for mean bias (the primary outcome in this review) and its standard deviations (SDs) across studies included for each subgroup of level of skin pigmentation and ethnicity. We calculated accuracy root-mean-square (Arms) and 95% limits of agreement based on pooled mean bias and pooled SDs for each subgroup. Results We included 32 studies (6505 participants); 27/32 (84.38%) in hospitals and none in people's homes. Findings of 14/32 studies (43.75%) were judged, via QUADAS-2, at high overall risk of bias. Fifteen studies measured skin pigmentation and 22 referred only to ethnicity. Compared with standard SaO2 measurement, pulse oximetry probably overestimates oxygen saturation in people with dark skin (pooled mean bias 1.11%; 95% confidence interval 0.29% to 1.93%) and people described as Black/African American (pooled mean bias 1.52%; 0.95% to 2.09%) (moderate- and low-certainty evidence). These results suggest that, for people with dark skin, pulse oximetry may overestimate blood oxygen saturation by around 1% on average compared with SaO2. The bias of pulse oximetry measurements for people with other levels of skin pigmentation, or those from the White/Caucasian group is more uncertain. The data do not suggest overestimation in people from other ethnic groups such as those described as Asian, Hispanic, or mixed ethnicity (pooled mean bias 0.31%, 0.09% to 0.54%), but this evidence is low certainty. Whilst the extent of mean bias is small or negligible for all the subgroups of population evaluated, the associated imprecision is unacceptably large (with the pooled SDs > 1%). Nevertheless, when the extents of measurement bias and precision are considered jointly in Arms, pulse oximetry measurements for all the subgroups appear acceptably accurate (with Arms < 4%). Conclusions Low-certainty evidence suggests that pulse oximetry may overestimate oxygen saturation in people with dark skin and people whose ethnicity is reported as Black/African American, compared with SaO2, although the overestimation may be quite small in hospital settings. The clinical importance of any overestimation will depend on the particular clinical circumstance. Pulse oximetry measurements appear accurate but imprecise for all levels of skin pigmentation. The evidence relates to clinician-measured oximetry in health care environments and may not be reflected in home pulse oximetry where other factors may also influence accuracy.

Background: The National Institutes of Health Stroke Scale (NIHSS) is widely used to measure stroke deficits and is deemed to be reliable when used by a range of professionals. Aims: This study aimed to establish the inter-rater reliability of the NIHSS when completed via telemedicine. Secondary aims were to explore if professional group, length of time since training and/or re-certification, frequency of use and reason for using the NIHSS influenced the inter-rater reliability. Methods: A total of 30 video clips, the equivalent of two whole patient assessments for each of the 15 NIHSS items, were analysed by a range of NIHSS-certified clinical participants. Of these, 10 were nurses and five were consultants. Kappa statistics were used to calculate the inter-rater reliability for each item, with additional data on the range of agreement of items. Data across group characteristics were compared to test hypotheses about factors that could impact reliability. Findings: Overall, the inter-rater reliability was found to be lower than anticipated, and there was a wide variation in ratings. Consultants tended to score better than nurses, and, counter-intuitively, stroke specialist staff and those who used the NIHSS more frequently tended to have poorer reliability than their counterparts. Total agreement on score was only achieved in five out of the 30 video clips (16.6%), with agreement better at either end of the scoring range (i.e. no deficit or worst deficit). These findings indicate that reliability of the NIHSS may be lower than anticipated. Conclusion: Further research is needed to better understand the poor reliability of the NIHSS, as this has implications for care decisions and patient outcomes.

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