Testing for Protein in Urine With a Dipstick

Introduction

The urine dipstick is an inexpensive and convenient way of screening for protein in the urine. It uses a special chemical (called tetrabromophenol blue) that changes different shades of green when it binds to albumin.

Getting a Protein Score

The urine dipstick reports protein in the urine ranging from “negative” to “4+” depending on the concentration of the albumin in the urine.

Negative ... Less than 15 mg/dL
Trace ......... 15 to 30 mg/dL
1+ ............... 30 to 100 mg/dL
2+ ............... 100 to 300 mg/dL
3+ ............... 300 to 1000 mg/dL
4+ ............... More than 1000 mg/dL

Interpreting the Results

The significance of a score may depends on how concentrated the urine is. A “2+” or higher usually means there is significant protein in the urine. A “trace” or “1+” result may or many not be significant depending on how concentrated the urine is. For example:

• Somebody dehydrated and producing very little urine (less that 1/2 liter per day) may have “1+” dipstick when there is relatively little protein loss (< 150 mg/day).
• Somebody losing 1000 mg of protein per day but with a dilute urine because they are drinking 5 liters a day, will have a “trace” results despite significant protein loss.

False Negatives Can Happen

Because urine dipsticks measure only albumin, they will not detect other proteins (such as antibody fragments) seen in certain kidney diseases. Also, because it is relatively insensitive for small amounts of protein loss (<300 mg per day), it is not a good screening for early diabetic kidney disease.