We studied the efficiency of the Natelson-type tube (NTT), which requires only 0.25 ml of blood, on 11 healthy adult volunteers (HAV) and 42 pediatric patients. Free flow venous and finger stick capillary specimens were taken simultaneously in duplicate. In patients, venous specimens were split to have Westergren method (WM) ESR and NTT ESR done simultaneously at 60 minutes. In the HAV group, NTT ESR (mean±SD) was 17.7±4.6 and 21.2±4.9 mm for venous and capillary samples respectively (p<0.05). The deviation from the mean of the duplicate values was 2.9±5.2% for venous and 4.9±4.4% for capillary blood. In patients, ESR(mean±SD) was 40.9±33.7 and 40.8±35.8 mm for the NTT and WM respectively (p>0.05). The graph shows the patients paired ESR, comparing the NTT with the WM. There is a linear regression y=0.97x and a correlation (r)=0.96, p<0.001. We conclude: 1) NTT ESR is reproducible, 2) NTT correlates very well with WM, 3) the correlation is linear, 4) NTT ESR is faster with capillary than with venous blood, 5) NTT is easy to use with small amounts of either venous or capillary blood thus of great value for neonates and small infants. Figure

figure 1

Figure 1