Table 2

Analysis of remote capillary versus venous phlebotomy in study subjects

TestNo of paired samplesPaired t-testCorrelationBland AltmanReference range of testInterchangeably in clinical setting based Paired t-test p>0.05Interchangeably in clinical setting based on r>0.8Interchangeably in clinical setting based on small Bias OR max 10% difference between testsPoint scoring for clinical acceptability
Mean of differenceSDSEM95% CITwo-tailed p valuer
(or rs)
95% CIBias (%)SD of bias (%)95% limits of agreement (%)
FromTo
Hb30−0.2011.492.10−4.49 to 4.090.92470.730.50 to 0.860.128.15−15.916.1115–151 g/LYesNoNo1
WCC29−0.691.160.22−1.14 to −0.250.00330.920.83 to 0.967.8812.99−17.5922.345.1–11.4×109/LNoYesNo1
Platelets3038.6739.807.2723.80 to 53.53<0.00010.930.86 to 0.97−15.7916.96−49.0317.44147–397×109/LNoYesNo1
HbA1c (%)31−0.050.200.03−0.12 to 0.0260.20240.980.97 to 0.99−0.803.43−5.927.534.0%–6.0%YesYesYes3
HbA1c
(IFCC)
32−0.472.050.36−1.20 to 0.270.20240.990.97 to 0.991.215.44−9.4611.8820–42 mmol/molYesYesNo2
Sodium36−2.222.570.43−3.09 to −1.35<0.00010.800.64 to 0.901.571.81−1.985.13133–146 mmol/LNoNoYes2
Potassium18−1.450.940.22−1.92 to −0.98<0.00010.750.44 to 0.9027.7714.19−0.0555.483.5–5.3 mmol/LNoNoNo0
Urea36−0.770.550.09−0.96 to 0.58<0.00010.960.93 to 0.9814.4610.15−5.4334.352.5–7.8 mmol/LNoYesNo1
Creatinine36−9.1414.382.40−14.00 to 4.270.00050.830.69 to 0.9111.6317.89−23.4346.7060–120 umol/LNoYesNo1
Bilirubin59−0.410.850.11−0.63 to 0.180.00050.980.97 to 0.995.8810.38−14.4726.230–20 umol/LNoYesNo1
ALP594.1055.927.28−10.47 to 18.680.25610.890.82 to 0.931.6119.90−37.3940.6130–130 U/LYesYesNo2
ALT59−0.703.660.48−1.65 to 0.260.78270.980.97 to 0.992.7513.20−23.1228.628–40 IU/LYesYesNo2
Total protein580.262.920.38−0.51 to 1.030.50320.860.78 to 0.92−0.373.92−8.077.3260–80 g/LYesYesYes3
Total IgE3512.2334.985.910.21 to 24.240.71040.990.99 to 1.00−34.8769.23−170.6−100.803–150 IU/molYesYesNo2
Vit D26−0.8912.722.50−6.02 to 4.250.72580.900.78 to 0.95−7.2653.68−112.597.9650–75 nmol/L—adequate
>75 nmol/L—optimal
YesYesNo2
CRP371.004.890.80−0.63 to 2.630.22130.990.99 to 1.00−0.414.30−8.838.00<100 mg/LYesYesYes3
Albumin*590.00†0.40700.75−0.61 to 0.85−0.226.15−12.2711.8435–50 g/LYesNoNo1
  • Values in bold symbolise significant difference between the tests by p<0.05, poor correlation (r or rs<0.8), or wide limits of agreement.

  • Point scoring of clinical acceptability—refer to figure 1 for algorithm for determination of clinical acceptability of capillary test.

  • Mean, SD, SEM, CI, r, rs, % bias, % limits of agreement to two decimal places).

  • Bias is the average of the differences between the two methods of blood sampling, expressed as a percentage %.

  • HbA1c here expressed as a percentage (%) and as a value in mmol/mol (IFCC unit).

  • *Non-parametric statistics applied for non-Gaussian distribution: Wilcoxon matched pairs signed rank test, non-parametric Spearman correlation rs.

  • †Result represents median of difference and not mean.

  • ‡Only 50% of potassium capillary samples were analysed due to haemolysis, and 72% of vitamin D capillary samples were analysed with the rest not processed due to insufficient blood in the capillary sample to process.

  • ALP, alkaline phosphatase; ALT, alanine transferase; CI, confidence interval; CRP, C reactive protein; Hb, haemoglobin; HbA1c, glycated haemoglobin; IgE, Immunoglobulin type E; r, Pearson’s correlation coefficient; rs, Spearman’s Rank correlation coefficient; SD, Standard deviation; SEM, SE of the mean of the difference; WCC, white cell count.