Evaluation of the ARKRAY AUTION Eleven reflectometer in detecting microalbuminuria with AUTION Screen test strips and proteinuria with AUTION Sticks 10PA strips.

OBJECTIVE

Albumin/creatinine and protein/creatinine ratios were measured with the ARKRAY AUTION Eleven reflectometer using AUTION Screen and AUTION Sticks 10PA strips, respectively, against quantitative Siemens Advia reference procedures from 368 patient urines, as an evaluation of their applicability for use in points-of-care and small laboratories.

MATERIAL AND METHODS

Direct reflectance measurements were utilized to estimate imprecision, as well as to suggest reclassification of ordinal scale categories into normoalbuminuria, microalbuminuria and macroalbuminuria groups (3.4 g/mol and 34 g/mol cut-off limits, corresponding to 30 mg/g and 300 mg/g creatinine in conventional units).

RESULTS

Analytically, ordinal scale albumin/creatinine ratios agreed in 86% of cases with those obtained from Advia measurements, resulting in a kappa coefficient of 0.79. Protein/creatinine ratios of the AUTION Sticks 10PA strip were classified into three groups at limits of 11.3 g/mol and 56.6 g/mol (100 mg/g and 500 mg/g in conventional units), with an agreement of 77% and a kappa coefficient of 0.65 against Advia procedures. To optimize clinical outcomes, cut-off reflectances of ordinal scale categories of AUTION Eleven were adjusted. The clinical specificity of detecting an increased albumin/creatinine ratio was then increased from 81% to 95%, with clinical sensitivity kept at 88% at the 3.4 g/mol limit of the reference procedure. Clinical specificity of the albuminuria field alone (at a clinical sensitivity of 88%) was only 73%. Adjustments to cut-off reflectances of the reported categories for protein/creatinine ratios increased clinical specificity from 54% to 94%, while losing clinical sensitivity from 97% to 89% only, with an improved concordance of 83% and a kappa coefficient of 0.75 against Advia measurements. The combination to creatinine measurements improved clinical specificity compared to 50% by the protein field alone. In economic terms, it is estimated that population screening for microalbuminuria using the AUTION Eleven reflectometer is cheaper than by quantitative albumin/creatinine measurements alone, based on the incidence of end-stage renal disease of 90 patients/million/year at the Northern Ostrobothnia Hospital District.