S. A. Sadjadi, MD
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Sadjadi S.; A New Range for the Anion Gap. Ann Intern Med. 1995;123:807. doi: 10.7326/0003-4819-123-10-199511150-00013
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Published: Ann Intern Med. 1995;123(10):807.
TO THE EDITOR:
The anion gap, the difference between routinely measured anions and cations of the serum, or NA+ − (Cl− + HCO3−), is a useful tool for deciphering simple and mixed acid-base disorders. When low, the anion gap can be used to indicate the presence of occult cancer or drug poisoning. The traditional normal value for the anion gap has been 12 ± 4 mEq/L (normal range, 8 to 16 mEq/L), values that textbooks continue to reiterate [1, 2]. However, as noted by Winter and colleagues  and others , the range for the anion gap is much narrower than previously thought because of the use of the ion-selective electrode. Thus, we retrospectively analyzed the serum anion gap in 222 patients with normal serum albumin and creatinine levels. We attempted to eliminate the effects of renal failure and hypoalbuminemia, two factors known to modify anion gap values. The results (mean ±SD) of our analysis were as follows: serum sodium level, 140 ± 2.7 mEq/L; potassium level, 4.6 ± 0.4 mEq/L; chloride level, 105 ± 4 mEq/L; CO2 level, 28 ± 2.9 mEq/L; and anion gap, 6.6 ± 2 mEq/L (range, 2.6 to 10.6 mEq/L). This range is almost identical to the value reported by Winter and colleagues .
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Print ISSN: 0003-4819 | Online ISSN: 1539-3704
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