Accuracy and Precision of the Pronto-7 for Noninvasive Hemoglobin Testing in An Outpatient Setting

Invasive blood draw and laboratory analysis for determination of total hemoglobin concentration (tHb) is routine in the outpatient setting. However, the method is time consuming, uncomfortable for the patient, and exposes caregivers to risks associated with needle sticks and blood exposure. In contrast, hemoglobin determination with Pulse CO-Oximetry (SpHb) allows for noninvasive and quick estimation of hemoglobin with a spectrophotometric finger sensor. Continuous SpHb has been validated in the ICU [1], surgery[2], and volunteers undergoing hemodilution, [3] but the accuracy of “spot check” SpHb devices has not been validated in the outpatient setting. Our objective was to compare spot-check SpHb and invasive point-of-care (POC) hemoglobin testing to tHb measurements from a laboratory hematology analyzer.

Study subjects were adult and pediatric subjects presenting to two outpatient clinics and one health screening event. A noninvasive hemoglobin test device (Pronto-7, software version 2.19, Masimo Corp. Irvine CA) and reusable finger clip sensor (rainbow 4D) was placed on the patient's non-dominant ring finger. The sensor was covered with an opaque shield to prevent optical interference. Two consecutive SpHb readings were obtained from each subject, detaching and reattaching the sensor between each measurement. Testing was conducted while patients were quiet and sitting upright. A venous blood sample was obtained by venipuncture of the median cubital vein of the non-dominant arm and a capillary sample was obtained by finger stick according to the manufacturer's directions for use. The venous sample was analyzed for reference tHb with a laboratory hematology analyzer (LH 780, Beckman Coulter, USA). The capillary sample was analyzed immediately following the finger stick with a POC device (HemoCue 201+, Hemocue, Cypress CA). The SpHb and POC tHb were compared to the laboratory tHb. Bias, standard deviation, and coefficient of variation (precision) were calculated.

A total of 474 subjects (37% male, 39 +/− 17 years of age) were enrolled, 431 (91%) from outpatient clinics and 43 (9%) from a community screening event. Subjects consisted of 246 (52%) healthy volunteers and 228 (48%) with one or more of the following conditions: high blood pressure, diabetes, high cholesterol, chronic obstructive pulmonary disease, or pregnancy. A total of 399 (84%) had light pigmentation, 71 (15%) medium pigmentation, and 3 (1%) had dark pigmentation. Reference tHb ranged from 8.6 to 17.4 g/dL. There were 877 SpHb measurements, 443 POC tHb measurements, and 473 reference tHb measurements. The mean bias and standard deviation of SpHb was −0.1 +/− 1.1 g/dL and of POC tHb was -0.1 and 1.6 g/dL. Using the first and second SpHb measurements, the precision of SpHb was 4.1%.

Noninvasive hemoglobin testing with the Pronto-7 had acceptable accuracy with similar bias and lower standard deviation than a widely available, POC tHB test device. The Pronto-7 has the potential to enhance patient care and caregiver safety in the outpatient setting.

Shah:Masimo Corp.: Consultancy, Honoraria, Speakers Bureau. Martinez:Masimo Corp.: Research Funding. Osea:Masimo Corp.: Research Funding.