Validation of point-of-care tests used at in-home assessments among older adults in primary care

Abstract

Background Diagnosing acute disease in older adults is challenged by vague and atypical symptoms. Point-of-care tests (POCTs) at home may improve diagnostics and clinical decision-making. We compared various POCT devices to routine testing in acutely ill older adults to assess their clinical reliability. Methods We enrolled participants aged 65+ years requiring acute in-home assessment with signs of acute conditions. Venous and capillary blood samples were collected and analysed on-site using POCT, while identical samples were transported and analysed in a routine laboratory. Agreement between POCT and laboratory testing was assessed using scatter plots with linear regression, Pearson’s correlation coefficient (PCC), limits of agreement, and Bland-Altman plots. Misclassification rates were calculated based on clinically meaningful cut-offs to assess POCT’s clinical reliability. Results We included 100 participants with a mean age of 81.6 (±8.4 SD) years. Strong correlation was found between POCT and routine measurements (PCC: 0.76–0.94 for capillary samples and 0.85–0.98 for venous samples). Venous samples showed higher PCC than capillary, except for neutrophils (0.93 for capillary, 0.89 for venous). Misclassification occurred in capillary samples for haemoglobin (10/62) and total WBC (6/50), while in venous samples, misclassification was observed for haemoglobin (4/54), total WBC (4/50), K+ (5/47), urea (5/47), and creatinine (3/42). No misclassification was observed for Na+. Conclusion POCT provides acceptable, clinically reliable measurements in acutely ill older adults, potentially enhancing diagnostics and treatments during in-home assessment. Venous blood testing is preferable due to a lower misclassification rate, but capillary blood remains a pragmatic alternative, despite higher variation and inaccuracy.