Soap and Pressure

Today I tested my blood sugar without washing my hands. The reading seemed highly odd, so I washed my hands and tried again. The second reading was far more realistic. But which one was more correct?

I recall once reading once that between two drops of blood, one should always use the first drop. But I wasn't sure of my memory on this, so I did a little online research and discovered this study investigating blood glucose readings under a variety of scenarios.

While the whole study is well worth reading, I thought I might provide the key details that were useful for me:
RESULTS Not washing hands led to a difference in glucose concentration of ≥10% in the first and in the second drops of blood in 11% and 4% of the participants, respectively. In fruit-exposed fingers, these differences were found in 88% and 11% of the participants, respectively. Different external pressures led to ≥10% differences in glucose concentrations in 5–13% of the participants.
We've all been instructed to wash our hands before taking a reading, but never could I have imagined that the readings would potentially be skewed beyond 10% of the clean-hands reading.

No surprises that fruit-exposed fingers showed an even greater propensity toward skewed readings - I have noticed that phenomenon, myself.

But most curiously, "external pressure" produced unreliable test results. In the study, "external pressure" consisted of wrapping the test subjects' fingers so that they were under increased pressure. So that means, if you've been clenching your fists or something, you'll end up with funny readings. Who would have thought? It makes intuitive sense, of course, but who pays attention to such things before testing their BG? Certainly not I.

The researchers' recommendations were as follows:
CONCLUSIONS We recommend washing the hands with soap and water, drying them, and using the first drop of blood for self-monitoring of blood glucose. If washing hands is not possible, and they are not visibly soiled or exposed to a sugar-containing product, it is acceptable to use the second drop of blood after wiping away the first drop. External pressure may lead to unreliable readings.
 From now on, I'm washing my hands.