How Much Hemolysis Is Acceptable When Undertaking Deep Lancing for Finger Stick Derived Capillary Plasma Glucose Measurement?

Analysis of common biomarkers in capillary blood in routine clinical laboratory. Preanalytical and analytical comparison with venous blood

OBJECTIVES

Remote self-collected capillary blood samples have been proposed as alternative to venous blood samples as an aid in telemedicine. The aim of this work is to compare the preanalytical and analytical performance of these two types of samples and to study the stability of common measurands in capillary blood.

METHODS

Capillary and venous blood samples were collected in parallel from 296 patients in serum tubes to analyze 22 common biochemistry magnitudes after centrifugation and in EDTA tubes to analyze 15 hematologic magnitudes. Quality of the preanalytical process was assessed applying the model of quality indicator. 24 h stability at room temperature was studied by obtaining paired capillary samples. A questionnaire of assessment was conducted.

RESULTS

Mean hemolysis index was higher in capillary samples compared to venous blood samples (p<0.001). Regression analysis and difference analysis showed no bias for all studied biochemistry parameters and hematologic parameters, except mean corpuscular volume (MCV), between capillary and venous blood samples. Regarding sample stability, percentage deviation was higher than the corresponding minimum analytical performance specification for ferritin, vitamin D, hematocrit, MCV, mean corpuscular hemoglobin concentration, platelets distribution wide, mean platelet volume and basophils. Finger pricking was perceived as less painful (p<0.05) than venipuncture in participants who undergo more than one blood test per year.

CONCLUSIONS

Capillary blood can be used as an alternative to venous blood for the studied parameters in automated common clinical analyzers. Cautious should be taken if samples are not analyzed within 24 h from the collection.

Preanalytical Challenges During Capillary Fingerstick Sampling Preclude Its Widespread Use in Adult Hospitalized Patients

OBJECTIVES

Patient compliance with laboratory testing is one of the most underrecognized challenges in developing a treatment plan for acute and chronically ill patients. The ability to offer alternatives to standard venipuncture blood draws would greatly increase a laboratory's ability to provide testing to patients and health care providers.

METHODS

We performed a prospective observational study on paired venous and fingerstick capillary blood samples from admitted patients undergoing vancomycin therapy. Paired specimens were analyzed for vancomycin and a basic metabolic panel (BMP: calcium, carbon dioxide, chloride, potassium, sodium, creatinine, glucose, serum urea nitrogen) on the core laboratory's automated chemistry and immunochemistry platforms.

RESULTS

A total of 59 paired fingerstick and venous blood specimens from 56 unique inpatients were analyzed. Paired samples were comparable for all the analytes tested with the exception of bicarbonate and potassium, which were significantly different among the capillary sample group. Patients required multiple fingers be lanced in 15% of cases to obtain sufficient blood to carry out the testing. Capillary sample rejection rates due to insufficient volumes were as high as 30% in the initial 30 patients enrolled in the study.

CONCLUSIONS

Vancomycin and the BMP, with the exception of potassium and bicarbonate, were determined to be analytically comparable. However, significant preanalytical issues should preclude laboratories and providers from more widespread adoption of fingerstick-derived capillary blood as an alternative sampling method except in the most extenuating of circumstances.