en Pediatric Gastroenterology Original Article Original Article <strong>Background</strong>: Pulse oximetry is a widely used non-invasive method for monitoring oxygen saturation (SaO₂) in pediatric patients. However, concerns have emerged about its accuracy across different skin tones, with darker pigmentation potentially leading to overestimation of arterial SaO₂.&nbsp;<br> <strong>Objectives</strong>: This study aims to evaluate the diagnostic accuracy of pulse oximetry (peripheral oxygen saturation [SpO₂]) in children with different skin tones, using arterial blood gas (ABG) analysis as the reference standard.&nbsp;<br> <strong>Methods</strong>: This prospective, cross-sectional study was conducted at a tertiary pediatric hospital in India over a 6-month period on 300 children aged 1 month to 18 years undergoing clinically indicated ABG sampling. Skin tone was classified using the Fitzpatrick scale, which divides children into three groups of 100, including light skin (types I&ndash;II), medium skin (types III&ndash;IV), and dark skin (types V&ndash;VI). Simultaneous SpO₂ and SaO₂ measurements were obtained, and mean difference (SpO₂&ndash;SaO₂), root mean square error (RMSE), and frequency of clinically significant overestimation (SpO₂ &ge;92% when SaO₂<88%) were analyzed. Multivariable regression was used to adjust for confounders.&nbsp;<br> <strong>Results</strong>: Pulse oximetry overestimated SaO₂ in all groups, with the greatest bias observed in the dark skin group (mean difference=1.9%, RMSE=2.6) compared to the light-skin peers (mean difference=0.8%, RMSE=1.6; P<0.001). Clinically significant overestimation occurred in 35% of dark-skinned children with SaO₂<88%, compared to 8% in light-skinned children (P=0.004). Dark skin tone (&beta;=1.04; P<0.001). and medium skin tone (&beta;=0.51, P=0.011) were the predictors of SpO₂ bias after adjusting for age and oxygen supplementation. Skin tone classification showed excellent inter-rater agreement (Cohen&rsquo;s &kappa;>0.88).<br> <strong>Conclusions</strong>: Pulse oximetry significantly overestimates arterial SaO₂ in children with darker skin tones, increasing the risk of unrecognized hypoxemia. These findings highlight a critical issue in pediatric monitoring and indicate the need for more inclusive device calibration, clinical vigilance, and confirmatory testing in dark-skinned children. Pulse oximetry, Diagnostic accuracy, Skin tone, Fitzpatrick scale, Pediatric hypoxemia, Oxygen saturation (SaO₂), Arterial blood gas (ABG) 339 344 http://jpr.mazums.ac.ir/browse.php?a_code=A-10-1365-2&slc_lang=en&sid=1 Janani MZ jenyzac81@gmail.com 100319475328460013038 0009-0004-3732-4735 No Department of Paediatrics, Postgraduate, Saveetha University (SIMATS), Chennai, India. Navin Umapathy navinu02@gmail.com 100319475328460013039 0009-0001-3538-0862 Yes Department of Paediatrics, Postgraduate, Saveetha University (SIMATS), Chennai, India. Maithree Mahesh Maithree.mahesh94@gmail.com 100319475328460013040 0009-0009-5836-9322 No Department of Paediatrics, Postgraduate, Saveetha University (SIMATS), Chennai, India. Devanand Gulab Chaudhary devagc94@gmail.com 100319475328460013041 100319475328460013041 No Department of Paediatrics, Postgraduate, Saveetha University (SIMATS), Chennai, India.