Lab Equations

Coefficient of variation

(SD/x)×100

Standard deviation

dilutions

Volume of specimen/(Volume of specimen+Volume of diluent)

diagnostic sensitivity

TP/(TP+FN)×100

diagnostic specificty

TN/(TN+FP)×100

positive predictive value

TP/(TP+FP)×100

negative predictive value

TN/(TN+FN)×100

Beers law

Cu​=(Au​/As​)×Cs

molarity

grams per liter/ grams molecular weight

normality

grams per liter/ gram equivalent weight

creatinine clearance

(urine creatinine x urine volume per 24hr) / (plasma creatinine) x (1.73/SA)

LDL cholesterol

total cholesterol - [HDL + (TG/5)]

Osmolality

1.86(Na) + (glucose/18) + (BUN/28)

Osmolal gap

measured - calculated osmolality

henderson-hasselbalch

pH = 6.1 + log[(HCO3-)/(pCO2 × 0.03)]

MCV

Hct x 10 / RBC

MCH

Hgb x 10/ RBC

MCHC

Hgb x 100/ Hct

Retics %

retics per 1,000 RBC / 10

Absolute relic count

retic % x RBC count

Corrected retic count

retic % x (pts Hct/norm Hct)

RPI

corrected retic count/ maturation factor

Corrected WBC

uncorrected WBC x 100 / 100 + nRBC

Cell counts

(cells counted x DF) / (VF)

RhIG Vials

(fetal cells counted / 2000) x 5000 = mL of fetal blood

divide by 30 for vials

Breakeven price per test

(total fixed costs + variable costs) / test volume

break-even test volume

total fixed costs / (average revenue per test - variable cost per test)