Estimating the intra- and inter-individual imprecision of manual pipetting.
BACKGROUND
Despite the importance of manual pipetting of fluids such as water, solutions, buffers, reagents, or biological samples in daily laboratory practice, the intra- and inter-individual imprecision of this activity has not been recently described in scientific publications.


METHODS
Twenty laboratory operators were randomly enrolled for this study. Imprecision of manual pipetting was estimated by asking each laboratory professional to dispense 1 mL, 100 μL or 10 μL of distilled water for 10 consecutive times with three certified pipettes into a 50-mL plastic container placed into a gravimetric balance. The weight of the water dispensed was systematically recorded for each of the 10 repeated attempts, and the inter- and intra-operator imprecision was finally calculated and expressed as coefficient of variation (CV%).


RESULTS
The mean intra-individual imprecision was 5.7% (range, 0%-11.8%) for pipetting 10 μL, 0.8% (range, 0.4%-1.9%) for pipetting 100 μL, and 0.2% (range, 0.1%-0.5%) for pipetting 1 mL. Overall, the mean inter-individual imprecision was 8.1% for pipetting 10 μL, 1.1% for pipetting 100 μL and 0.4% for pipetting 1 mL. A significantly inverse correlation was found between intra-individual pipetting imprecision and the amount of water dispensed (r = -0.80; p<0.001). No significant correlation was observed between individual pipetting performance and sex, age, qualification, and years of experience in the laboratory.


CONCLUSIONS
The results of this study show that manual pipetting is plagued by a considerable intra- and inter-individual imprecision, which is inversely correlated with the amount of fluid dispensed.
.
Giuseppe
http://orcid.org/0000-0001-9523-9054
G
Lippi
.
Gabriel
G
Lima-Oliveira
.
Giorgio
G
Brocco
.
Antonella
A
Bassi
.
Gian Luca
GL
Salvagno
D000328:Adult; D000368:Aged; D019411:Clinical Laboratory Techniques / Q000295:instrumentation*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011786:Quality Control; D015203:Reproducibility of Results
imprecision; pipette; pipetting; quality; variability