Original Articles
November 1968

Neutrophil Alkaline Phosphatase Activity

Arch Intern Med. 1968;122(5):412-416. doi:10.1001/archinte.1968.00040010412007

Neutrophil alkaline phosphatase (NAP) activity is increased during pregnancy. This study confirms the clinical impression that oral contraceptive hormones may increase NAP. Eighty-four healthy female subjects receiving any one of four commonly prescribed oral contraceptive hormone preparations demonstrated a mean increase of approximately three times values determined in 61 control subjects. Peak levels were noted during the final week of the menstrual cycle. The NAP returned to normal during the first week of the subsequent menstrual cycle. Oral administration of either of the constituents of a selected oral contraceptive (mestranol, 0.1 mg, or norethindrone, 2 mg daily) for 20 consecutive days also significantly increased NAP over control levels. The diagnostic usefulness of the NAP reaction in clinical medicine may be minimized as more of the general female population use oral contraceptive hormones.