Urine Metabolic Screening Test

battery of tests that is performed on urine specimens to detect the possibility of a metabolic disorder

not specific and are used only as screening tests

1) Ferric Chloride Test:

Materials and Methods: 1 ml FeCl3 reagent+ 10 drops urine, shake and observe result

Condition/Substance Result

Acetoacetic Acid Red-brown

Alkaptonuria (homogentisic Acid) Blue-green (transient)

p-Aminosalicylic acid Purple-brown

Bilirubin Blue-green

Histidinemia Blue-gray to green

Lactic Acidosis Gray

MSUD Green to gray

Melanin Gray ppt to black

Methionine Malabsorption Purple to red-brown

Phenothiazines Purple brown

Phenylketonuria Blue green

Pyruvic acid Deep yellow

Salicylates Purple

Tyrosinemia Green (fades rapidly)

Xanthurenic acid Dark green to brown

2) Benedict’s Test

test for the presence of monosaccharides Glucose Fructose

test for the presence of some disaccharides Maltose

test for the presence of aldehydes Benedict’s reagent can be used to test for presence of glucose in urine

Indication of diabetes Heating a Benedict’s solution mixed with monosaccharides will produce a reddish-orange color Benedict’s Reagent Contains blue copper(II) sulfate (CuSO4) The copper oxide is insoluble in water and so it precipitates Contains NaOH and tartaric acid Color of the final solution ranges from green to brick red depending on how many copper(II) are

present

Methodology: 5-mL of Benedict’s reagent in a test tube, Heat to boil, then add 8 drops of urine, Boil again, after 2 minutes read the results.

No precipitate Negative

Green a trace

Yellow +

Orange ++

Red +++

Results noted as:(-) --> BLUE(+) --> GREEN to YELLOW(++) --> YELLOW to BROWN(+++) --> BROWN to ORANGE(++++) --> ORANGE to RED

Benedict’s reagent: Deep-blue alkaline solution of copper sulfate, sodium hydroxide, and tartaric acid

Urinary Substances and Clinical Syndromes Associated with Reducing Substances

Reducing Substance

Clinical State

Drugs Ascorbic acid, chloral hydrate, tetracyclines, sulfonamides, chloramphenicol

Fructose Fructosemia, essential fructosuria, hereditary fructose intolerance

Galactose Galactosemia, classic and variant (galactokinase deficiency)

Glucose Diabetes mellitus, renal glycosuria, Fanconi’s Syndrome, Wilson’s Disease

Homogentisic acid

Alkaptonuria

Lactose Lactase deficiency, lactose intolerance, newborn

Phenolic compound

Phenylketonurias, tyrosinosis

Xylose Excessive fruit intake

Xylulose Pentosuria

3) Cetyltrimethylammonium Bromide Test (CAB)

Turbidometric technique Uses quaternary ammonium compounds e.g. CAB Used for both qualitative and quantitative determination of urinary mucopolysaccharides and

glycosaminoglycans in various forms of mucopolysaccharidoses

Procedure: 5 ml of urine in a test tube, allowe to stand at room temperature, add 1 ml of CAB reagent, Test tube observe for 30 minutes.

Negative : no turbidity observed Positive : positive turbidity observed

4) Ninhydrin Test

Ninhydrin Reagent Solution:

Ninhydrin: 0.35g

ethanol or acetone/butanol

so-propanol: 100ml

Methodology: 1 ml Ninhydrin reagent + 3 drops of urine, Warm for 30 secs. In water bath.

Observe color:

Violet: alpha amino acid

bluish-purple solution: presence of amino acids in urine

yellow-orange: presence of proline

5) Nitroprusside Test

Used in the screening of cystinuria, homocystinuria and β-mercaptolactate cysteine disulfiduria

Methodology: 5 mL of Urine add 5 drops of Conc. NH4OH (ammonium hydroxide) then Mix and

then add 2mL of 5% NaCN (Sodium cyanide) . Stand for 10 min, add 4 drops of Sodium Nitroprusside. Mix and Observe Color Change

Positive Test Result

+ - pink

++ - pinkish

+++ - purple

++++ - dark purple