Comparison of the NBM 200 non-invasive haemoglobin sensor with Sahli's haemometer among adolescent girls in rural India

Abstract

Objective: The study objective was to compare haemoglobin measurements between the NBM 200 (non-invasive haemoglobin sensor) and Sahli’s hemometer in adolescent girls in a rural Indian setting. Methods: Participants included girls aged between 13 to 17 years from 34 villages in Tuljapur and Lohara blocks of Osmanabad district, Maharashtra, India. Haemoglobin (Hb) measurements from the non-invasive sensor (NBM 200) were compared with measurements obtained from Sahli’s hemometer using Bland-Altman plot, Spearman correlation coefficient, sensitivity, specificity, and area under the receiver operating characteristic curve analysis (AUROC). Results: Paired measurements from both methods were obtained from 766 adolescent girls (N=766). Haemoglobin levels estimated by Sahli’s hemometer ranged from 5.0 g/dL to 14.0 g/dL (mean: 10.1 g/dL, standard deviation (SD): 1.41), whereas measurements obtained from the NBM 200 ranged from 9.5 g/dL to 15.2 g/dL (mean: 12.8 g/dL, SD: 1.42). The Bland-Altman analysis indicated a mean difference of -2.70 g/dL (95% Confidence Intervals: -2.84 to -2.55) demonstrating an overestimation of Hb measurement by the NBM 200 compared to the Sahli’s hemometer measurements. The NBM 200 showed low sensitivity (23.6%) and moderate specificity (61.8%) for the diagnosis of anaemia. The AUROC score was 0.43 indicating an underestimation of anaemia in our study population by the NBM 200. Conclusion: Haemoglobin measurements obtained from the NBM 200 were consistently higher leading to an underestimation of anaemia prevalence compared with Sahli’s hemometer estimates among adolescent girls in India.