INFOCUS Urine Dipstick Testing: Everything You Need to Know BY JAMES R. ROBERTS, MD The latter function is disrupted in a variety of diseases. hink of all the times you order The normal USG ranges from Turinalysis each shift. It seems 1.003 to 1.030. USG less than 1.010 to be a straightforward test, and is suggestive of relative hydration, most physicians think they are and values greater than 1.020 in- well versed in the interpretation dicate relative dehydration. Patho- of the results: You give it a glance logic conditions that increase the and make a decision. The dipstick USG without regard to hydration analysis, the microscopic exam, included glycosuria and syndrome and other information gleaned of inappropriate antidiuretic from a UA make their way into hormone secretion (SIADH). decision-making for a variety of Osmolality is the more important diagnostic, therapeutic, and dis- parameter to measure in such position issues. Like most things cases. A decreased USG, also learned in detail many years known as dilute urine, is associated ago, the interpretation of the UA with diuretic use, diabetes insip- should be revisited on a regular idus, adrenal insufficiency, aldoster- basis. onism, or a plethora of conditions I find myself thinking I know James R. Roberts, MD causing impaired renal function. Clear urine with a dipstick strongly positive for blood usually means everything about a certain test It should be noted that the myoglobinuria. In such cases, the microscopic analysis would be negative only to find that the guidelines for RBCs. Significant myoglobinuria can produce acute renal failure. purpose of the kidney is to concen- have changed, technology has ad- trate urine when needed. Many vanced, and previously held dogma honored ritual of cleaning the ex- fistula. Certain foods such as as- renal diseases alter this concentrat- is now relegated to the status of ternal genitalia in women has little paragus or beets and a variety of ing function and result in a fixed misconception. When one con- or no proven benefit, although it is medications can change the odor specific gravity — about 1.010, the siders the complexity of the UA, it commonly emphasized. Some re- or color of urine. Myoglobin colors specific gravity of the glomerular is obvious that this is not a simple views put the contamination rates the urine brown, carrots can pro- filtrate. This is known as isosthen- test. The intricacies and subtleties as similar in specimens obtained duce a deep yellow color, and uria, a condition seen, for example, are actually quite amazing. This with or without prior cleaning. pseudomonas infections, propofol, in patients with renal dysfunction month’s column focuses on dip- (Arch Intern Med 2000;160[16]: and amitriptyline may give a blue/ because of sickle cell disease. stick testing, and next month’s will 2537.) Urine should be refrigerated green hue to the urine. Urinary pH: The urine pH gener- review urine microscopy. if it cannot be examined for more Dipstick Analysis: The accuracy ally reflects the serum pH, but the than two hours because delayed of detecting microscopic hematuria, primary and normal function of the kidney is to acidify the urine. Nor- Urinalysis: A Comprehensive analysis can produce unreliable significant proteinuria, or urinary Review results. tract infection is a subject of much mal serum pH is 7.4, but the normal Simerville J, Maxted WC, Physical Properties: A variety interest and practicality to emer- urinary pH ranges from 4.5 to 8. Pahira JJ of foods, medications, metabolic gency physicians. The urine dipstick Because of normal metabolic activ- Am Fam Physician products, and infections can cause has false-positive and false-negative ity, the generally accepted normal 2006;74(7):1096 abnormal urine colors and odors. results, and a list is presented in the pH of urine is about 5.5 to 6.5. The Normal urine is clear and light yel- table. It also should be noted that kidney cannot acidify the urine in The authors of this nifty review dis- low in color. Concentrated urine the commonly used urine dipstick renal tubular acidosis (RTA), so cuss the value of the standard UA produces a darker color, a common has a finite lifespan, should be kept the urine can be alkaline while the for diagnosing many urinary tract finding in the morning after in a closed container, and should patient’s serum demonstrates a conditions, including malignancy overnight water restriction. Cloudy not be constantly exposed to air. metabolic acidosis. and metabolic issues. The review urine can be normal, usually Testing with outdated and improp- The urine pH can be related to covers the correct method for per- caused by precipitated phosphate erly stored materials can lead to er- diet. Acid urine can be the result forming urinalysis and highlights crystals in alkaline urine. Significant roneous results. Dipstick testing is of ingesting fruits (hence the use the importance and diagnostic pyuria also can cause clouded quite helpful, serving as a screening of cranberry juice) that acidify the value of a number of abnormal res- urine. test for some conditions and a urine. Diets high in citrate and in ults found on the dipstick and with Urine clarity is a good but not definitive test for others. Dipstick citrus fruits, legumes, and veget- microscopy. Information gained for infallible guide to the presence or testing in complicated cases or seri- ables can cause alkaline urine. Meat the UA is termed invaluable by absence of UTI. (Pediatrics 2000; ous disease must be correlated with eaters tend to have more acidic these urologists from Georgetown 106[5]:E60.) Many believe that microscopy and clinical parameters. urine, and vegetarians tend to have University. odoriferous urine is a sign of infec- Urine Specific Gravity: Urine alkaline urine. Alkaline urine in the Specimen Collection: A mid- tion, but it can simply represent a specific gravity (USG) generally presence of a documented UTI stream clean-catch technique is concentrated specimen or a partic- correlates with the urine osmolality. may suggest infection with a ur- usually adequate for most men and ular diet. Urine that has prolonged The most useful information de- ea-splitting organism (such as pro- women and in most ED situations. bladder retention time can develop rived from the USG is insight into teus). Triple phosphate crystals These authors say (and many an ammonia-like odor. A fecal smell the patient’s hydration status and (magnesium ammonium phosphate would disagree) that the time- in the urine suggests a GI-bladder the concentrating ability of kidneys. crystals) in alkaline urine can form 14 EMERGENCY MEDICINE NEWS | MAY 2015 LWW-EMN_May 2015_Layout.indd 14 15/04/15 10:31 PM INFOCUS INFOCUS a staghorn calculus. Uric acid concentration to the required Iodinated radiocontrast agents stones form in an acidic urine. cutoff deemed positive, 3 plus or and a highly alkaline urine may Hematuria: The strict definition more on the dipstick. The authors turn the dipstick falsely positive. of hematuria by the American Uro- note that up to 20 percent of pa- Glycosuria: Glucose is nor- logical Association is the presence tients with a gross hematuria have mally filtered by the glomer- of three or more red cells per high- a urinary tract malignancy, so this ulus, but this substance is then powered field in two of three urine condition requires a full workup. almost completely absorbed in samples. The urine dipstick is used Hematuria, in the absence of pro- the proximal tubule. Glycosuria to test for the peroxidase activity teinuria or RBC casts, suggests a results when the amount of of erythrocytes, not for the actual pure urologic cause (stones/ filtered glucose exceeds the presence of the physical RBC. Of malignancy) for hematuria. kidney’s ability to resorb, mak- course, myoglobin and hemoglobin Proteinuria: Healthy kidneys ing glycosuria an abnormal produce a positive dipstick for limit the protein permeability of finding. The blood glucose is hematuria because these sub- the glomerular capillaries, but dis- usually at least 180 mg/dL to stances also will catalyze this reac- eased kidneys allow more protein be detected by the dipstick. tion; these are the end-products of to be filtered so proteinuria is a Ketonuria: It is not normal hemolyzed RBCs or muscle break- hallmark of a variety of renal dis- to find ketones in the urine. down. High doses of vitamin C will eases. Blood proteins are normally Ketones are the product of fat inhibit this process, and can inval- filtered and then reabsorbed by metabolism that is commonly James R. Roberts, MD The eyeball analysis of dipsticks has idate the dipstick for this test. This the proximal tubule cells. Urinary encountered in uncontrolled been replaced with machine reading. also holds true for stool guaiac proteins include primarily albumin, diabetes. Some ketonuria can This device reads the dipstick and testing; vitamin C can produce a but some serum globulins are de- occur normally in patients on a transfers the results directly to an false-negative occult blood in tected. The actual definition of pro- carbohydrate-free diet electronic medical record. stool. It has always been standard teinuria is the excretion of more (high-protein weight loss diets) that a positive dipstick for blood in than 150 mg of protein per day. and occasionally with starvation or reagent on the dipstick is quite the absence of RBCs by micro- Patients with early renal disease a prolonged fast. sensitive to environmental air, so scopy is indicative of myoglobin- may have microalbuminuria. Early Nitrites: There is a difference this test is the one that is most uria or hemoglobinuria, not true diabetic nephropathy may not be between nitrates and nitrites.