Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (280 page)

The diagnosis of mild preeclampsia
is made in a previously normotensive woman with new onset of hypertension and proteinuria after 20 weeks of gestation (BP ≥140/90 and proteinuria ≥0.3 g in 24 hours or a protein: creatinine ratio ≥0.3 mg/mg). (Collect urine by catheter if membranes have ruptured or in presence of vaginitis.)

   Alternate tests: >1+ on dipstick on two occasions >6 hours but <1 week apart
or
two specimens ≥1+ by dipstick 6 hours but <1 week apart
or
a single specimen ≤2+ by dipstick

   Increased serum inhibin A (at 15–20 weeks) and activin A (at approximately 30 weeks) may indicate preeclampsia and preterm labor
³
.

The diagnosis of severe preeclampsia
is made with a blood pressure >160/110 on two occasions at least 6 hours apart, proteinuria of >5 g/day, and persistent visual or mental abnormalities.

Additional tests:

   Proteinuria >3+ on dipstick on two occasions >6 hours apart or significant new-onset proteinuria ≥3.0–5.0 g/24 hours or >3+ by dipstick on two occasions.

   Oliguria—urine output ≤500 mL/24 hours.

   AST or ALT abnormal with persistent right upper quadrant or epigastric pain.

   CBC may show a platelet count <100,000/μL and increased HCT.

   Blood smear may show schistocytes if microangiopathic hemolysis is present.

   Serum uric acid is increased in virtually all cases of preeclampsia; correlates with disease severity.

   Serum creatinine >1.2 mg/dL. Creatinine clearance is decreased, causing increased BUN and creatinine.

   BUN may be normal unless the disease is severe or there is a prior renal lesion. (BUN usually decreases during normal pregnancy because of the increase in the GFR.)

   Urinalysis: RBCs and RBC casts are not abundant; hyaline and granular casts are present.

   Histology: Biopsy of kidney is pathognomonic (swelling of glomerular and mesangial endothelial cells) and also rules out primary renal disease or hypertensive vascular disease.