Bayer HealthCare Rapidlab 800 - Manual (Page 654)

IĆ34 800 Series Operator's Manual
Calcium Adjustment for pH
Ionized calcium values are dependent upon sample pH. The calcium value adjusted
to pH of 7.40 reflects the true ionized calcium concentration of blood normalized
to pH 7.40. Calcium is corrected according to the following equation.
30
adjusted Ca ++ = Ca ++ measured
×
10 –0.178 [required pH –measured pH]
Calcium value is adjusted only when pH, at 37
°
, is between 7.2 and 7.7, since no
reliable, published, clinical data is available outside that range.
Anion Gap
The anion gap (AnGap) is an approximation of the difference between unmeasured
cations and unmeasured anions. Historically, several formulas have been used to
mathematically approximate the balance of these unmeasured ions.
An anion gap result is of twofold value in a clinical laboratory. Primarily, abnormal
anion gap results indicate electrolyte imbalance or other conditions where
electroneutrality is disrupted, such as seen with diabetes, toxin ingestion, lactic
acidosis, or dehydration. Secondly, the anion gap result is useful for quality
assurance of laboratory results. If an increased or decreased anion gap result is
calculated from a non-diseased individual this indicates the possibility to one or
more erroneous electrolyte results.
The 800 system calculates the anion gap based on the following analytes:
AnGap = (Na + + K + ) – (Cl – + HCO
3
– act )
The bicarbonate (HCO
3
– ) in the above formula is also derived using the
Henderson-Hasselbalch equation for determining bicarbonate calculations.