Required section · Section 4 of 6

Work the related values

Work from declared inputs: MCV = 27.0 ÷ 3.10 × 10 = 87.1 fL; MCH = 9.1 ÷ 3.10 × 10 = 29.4 pg; MCHC = 9.1 ÷ 27.0 × 100 = 33.7 g/dL. The same case gives absolute neutrophils = 8.5 × 0.55 = 4.675, or 4.7 × 10^9/L after the stated rounding; plateletcrit = 165 × 10.8 ÷ 10,000 = 0.1782%, or 0.18% if that is the analyzer’s defined calculation and rounding.

A limited rule-of-three screen compares hematocrit with hemoglobin × 3 only as a prompt to investigate. It is expected to fail with microcytosis, macrocytosis, hypochromia, abnormal morphology, and marked anisocytosis; it neither validates a CBC nor justifies rejecting a result.

Worksheet calculates MCV 87.1 fL, MCH 29.4 pg, MCHC 33.7 g/dL, absolute neutrophils 4.7 times 10 to the ninth per liter, and plateletcrit 0.18 percent from the case inputs. — Figure 1Worked calculations for red-cell indices, absolute neutrophil count, and plateletcrit, with inputs and units shown.

Knowledge checks

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Knowledge check 1

Which calculation gives plateletcrit in the case when the local analyzer defines plateletcrit as PLT × MPV ÷ 10,000?

Choose one option.

165 × 10.8 ÷ 10,000 = 0.1782%, reported 0.18%

9.1 ÷ 27.0 × 100 = 33.7 g/dL

Knowledge check 2

The limited rule-of-three screen compares hematocrit with hemoglobin × 3. A mismatch in this case should first be understood as:

Choose one option.

A prompt to investigate microcytosis, macrocytosis, hypochromia, abnormal morphology, or marked anisocytosis, not proof that the CBC is invalid.

Automatic proof that the CBC must be rejected and recollected.

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