Measurement of iron is important for identifying both low and high iron levels in the body. Measuring a protein in the blood called ferritin is currently the easiest way to determine a patient's iron status. However, the test requires a blood sample that is be sent to the laboratory for measurement, which can cause delays in obtaining the result. The investigators are testing whether a point of care device that measures ferritin levels using a capillary blood sample is accurate compared to current methods of testing. This could allow measurement of ferritin immediately in the clinic with only a drop of blood, and enable treatment decisions based on these results.
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
DIAGNOSTIC
Masking
NONE
Point of care test that uses capillary blood sample from finger to determine ferritin level
Point of care ferritin detection accuracy
The proportion of subjects where the difference between the two different methods is less than 15; this will be measured by calculating the difference between the two results. The proportion for the absolute difference between the two measurement methods on the same subject that is less than 15 ng/mL will be calculated. Non-inferiority test for one proportion will be performed to examine, if, the proportion is greater than 95%, where the test p value and the one-sided 97.5% confidence interval will be reported. An interim analysis will be performed after the first 50 subjects are enrolled to test the assumptions made.
Time frame: Within 12 hours of standard testing
Distribution of the differences between ferritin level as measured by the standard test and POC test
Distribution of the differences between the two measurement methods using the normality test, mean difference and its 95% CI, and outlier detection; other methods may be used as appropriate
Time frame: Within 12 hours of standard testing
Comparison of the differences between ferritin levels as measured by the standard test and POC test in a Repeated Measures Design
Applies to patients who have multiple measurement points during study follow-up. The differences in ferritin levels between the two methods will be studied using a mixed model to account for the between-subject variation and the within-subject variation. The mean difference and its 95% CI, the Bonferroni-adjusted p-values and the plot of mean vs time will be reported.
Time frame: Within 12 hours of standard testing
Agreement between testing methods in patients who have been assessed at least twice
Applies only to patients with at least two repeated measures. Agreement between the two measurement methods will be quantified and summarized using probability of agreement.
Time frame: Within 12 hours of standard testing
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Diagnostic accuracy of the new measurement method
The Receiver Operating Characteristic curves (ROC) analysis will be performed to report the diagnostic accuracy for the new measurement method. The optimal cut-off value and the associated accuracy measures (sensitivity, specificity, predictive values and etc.) will be reported.
Time frame: Within 12 hours of standard testing