Revisiting a Common Lab Test: A Review of Urinalysis & Urine Culture. Beth Warning, MS, MLS(ASCP) cm

Transcription

1 Revisiting a Common Lab Test: A Review of Urinalysis & Urine Culture Beth Warning, MS, MLS(ASCP) cm

2 About the Speaker Bench tech experience in hematology, hemostasis, urinalysis, toxicology, and chemistry in a large multisystem medical center Program Director of a hospital based MT Program as well as Safety and Education Coordinator Lab Director of Immediate Response Lab and Critical Access Lab MLS instructor at University of Cincinnati for online and on campus students

3 Objectives Describe the pre-analytical requirements for urine and urine culture. Identify current practices in analytical testing of urine. Correlate biochemical findings with select clinical conditions. Describe the process of urine culture for select patient populations.

4 Purpose When is a urinalysis assay recommended? Suspected urinary tract infection Suspected non-infectious renal condition o Hypertension o Renal calculi o Renal disease o Kidney disease

5 Pre-Analytical Considerations Patient education and instruction Is the patient provided collection information? Type of collection May vary with the test request

6 Pre-Analytical Considerations Random collected at any time of day, no patient preparation First morning - bladder incubation of 4 8 hours, more concentrated Midstream clean catch - preferred for C&S orders, requires instructions for cleansing urogenital area Catheterized collection invasive and risks contamination with urethral flora, used for C&S Timed all voided samples for 8-24 hours, requires patient instructions

7 Pre-Analytical Considerations Primary urine collection container requirements: Allow for ease of collection, ease of sampling, appropriate for uropathogen detection For patient convenience, have a wide opening and base to avoid accidental spills Be equipped with an air tight, secure cap to prevent leakage or contamination Hold 50 ml minimal volume Sterile containers are required for C&S Non-sterile collections should be tested within 2 hours or refrigerated at C

8 Pre-Analytical Considerations Secondary urine containers Aliquot of primary specimen into a vacuum tube Potential decrease in casts due to disintegration during vacuum aspiration Potential release of RBCs and WBCs from disintegration of cellular cast Preservatives Extend testing time up to 72 hours Common preservatives include tartaric acid, boric acid, and chlorhexidine Requires correct fill volume

9 Pre-Analytical Considerations Quantity of specimen collected 3L for 24 hour testing Identification and labeling of the specimen Date and time of collection Storage and handling of specimen Amber colored containers for light sensitive analytes: phorphyrins or urobilinogen

10 Chemical Analysis Proteinuria increased urine protein excretion >150 mg / 24hrs Protein is filtered through the capillaries of the glomerulus Considered benign when found in healthy individuals o dehydration, stress, fever, inflammation, exercise o normal excretion 20% immunoglobulins, 40% albumin, 40% Tamm Horsfall protein Protein >100 mg/dl in a healthy individual may be transient, repeat testing is recommended Persistent proteinuria is present in glomerular disease o minimal change disease, focal segmental glomerulonephritis, IgA nephropathy, preeclampsia, diabetes, HCV, lung or GI cancers o confirm with quantitative 24-hour measurement

11 Analytic Variables in Chemical Analysis Obtained on 3/2/16 from Dipstick analysis for protein Typically uses the dye binding methodology with colorimetric reaction in the presence of protein False positive tests o ph>7.5 o oversaturation of the dipstick pad o drug interference o increased cellularity due to RBCs, WBCs, bacteria, or semen and vaginal secretions

12 Chemical Analysis Glucosuria- increased urinary glucose Kidneys release glucose during gluconeogenesis 100% reabsorption by the proximal renal tubules Excretion when renal threshold > mg/dl; varies with age, gender, and body mass Common in premature infants as filtration of glucose is difficult for the immature nephron Conditions where glucosuria is observed: o diabetes o acromegaly o thyrotoxicosis o liver disease o pancreas disease

13 Analytic Variables in Chemical Analysis Glucose Detection Method Glucose oxidase breakdown to gluconic acid and hydrogen peroxide yielding a colorimetric reaction in the presence of a chromogen Dipstick analysis Optimal temperature and ph necessary for enzymatic reaction False positive reactions may be due to excess vitamin C intake, reducing the hydrogen peroxide in the oxidase reaction Clinitest tablet is a semi-quantitative test for reducing sugars and is not widely used due to increased newborn screening

14 Chemical Analysis Ketonuria is the presence of ketone bodies in the urine Ketones: products of fatty acid metabolism released into bloodstream and filtered by the glomerulus Three types (no single test for all three): o o o Acetoacetate B-hydroxybutyrate acetone Ketonuria with plasma concentrations >0.2mM Present in diabetic ketoacidosis and starvation

15 Analytic Variables in Chemical Analysis Ketone Detection Method sodium nitroprusside colorimetric reaction Dipstick Analysis False positives associated with o specific medication o deeply pigmented urine Acetest reagent tablet is available for semi-quantitative testing

16 Chemical Analysis Bilirubinuria released due to excessive hemoglobin breakdown in the live; filtered and excreted by the glomerulus Detected when renal threshold >0.02 mg/dl Associated with conditions such as bile obstruction liver disease obstructive jaundice

17 Analytic Variables in Chemical Analysis Bilirubin Detection Method Diazonium salt exposed to bilirubin in an acid environment to yield a colorimetric reaction Dipstick Analysis False positive interference from medication Ictotest is not widely used

18 Chemical Analysis Clinical and Laboratory Standards Institute (CLSI) recommendations: Confirmatory chemical urinalysis tests detect the same substance with the same or greater sensitivity and/ or specificity. Repeating a reagent strip reaction or analysis is not a confirmatory test. Many of the historical confirmatory chemical urinalysis tests such as sulfosalicylic acid (SSA) test for protein and the tablet test for bilirubin etc., may not be relevant to current laboratory practice. (Urinalysis; Approved Guideline Third Edition, 2009 GP16-A3)

19 Microscopic analysis Manual provides rough estimate of cellular and non-cellular elements Can use light microscopy, phase contrast, or polarized microscopy for detection Average length of slide review is 6 minutes per patient Automated methods incorporate microscopic evaluation based on: Flow cytometry Auto-particle recognition Digital imaging Manual vs automated quantification 5 RBCs/hpf ~ 26 rbc/ul 5 SEC/lpf ~ 1.95 SEC/uL

20 Urine Culture The infectious process involves bacteria that can: Attach to mucosal membranes or glycolipids of the bladder with fimbriae Possess hemolysins, capsular polysaccharides, or cytotoxic necrotizing factor proteins Have increased invasiveness through hemolysins Colonize by ascending entry through the urethra into the bladder Host defenses Acidic nature of urine, high urea content, and high osmolality prevent colonization Mucopolysaccharide lining deters adhesion Secretory defense through IgA Normal flora form barriers to prevent colonization with foreign bacteria

21 How Can Infection Develop? Periurogenital spread from the normal flora of the urethra; anal or genital proximity Hematogeneous spread secondary to systemic sepsis Ascending spread via the urethra due to decreased urinary flow, catheterization, urethral obstruction, or pregnancy Obtained 3/2/16 from

22 What Type of Infections Develop? Cystitis is a lower urinary tract infection Symptoms of dysuria, increased urinary frequency and urgency, incontinence Pyelonephritis is an upper urinary tract infection Same symptoms as cystitis but also flank pain, fever, chills, increased WBC, nausea and vomiting

23 What Types of Infections Develop? Nonspecific UTI present with mental status change in the elderly Uncomplicated UTI occurs without colonization of the mucosa membranes Complicated UTI occurs in patients with preexisting conditions such as immunocompromised or structural malformation of the urogenital tract Asymptomatic UTI occurs in the elderly without typical symptoms but >100,000 CFU upon culture

24 Urine Culture Leukocyte esterase positive for WBCs on the dipstick Microscopic pyuria >10 WBCs/hpf Nitrite positive on the dipstick Microscopic hematuria (presence of RBCs) Microscopic bacteria >2+ Colony count value from 10 2 to > 10 5 / ml Cannot be the only criteria for ruling UTI in or out

25 Urine Culture and Organism ID Gold standard remains urine culture and colony count Common organisms Escherichia coli Klebsiella pneumoniae Proteus mirabilis Staphylococcus saprophyticus

26 Urine Culture Routine culture Gram stain with the presence of any bacteria observed over ten OIF 0.01 ml calibrated loop streaked perpendicular for colony count onto 5% SBA & Mac with a hour incubation at 37 C

27 Urine Culture Females present most frequently with cystitis Positive leukocyte esterase >10 WBCs/hpf On culture, growth will differentiate infection Cystitis > 1000 cfu/ml Pyelonephritis >10,000 cfu/ml Asymptomatic bacteriuria >100,000 cfu/ml

28 Recurrent Infections in Females Defined as 2-4 recurrences within one year Reinfection occurs by the same pathogen Demographic population includes premenopausal, sexually active, and otherwise healthy women Culture reveals >10 2 CFU/mL

29 Infection in Males Infrequently encountered, complicated UTI Symptoms include dysuria, urinary frequency, and fever Cystitis associated with prostatitis, epididymitis, urethritis and catheter use Enteric bacterial pathogens; most commonly E. coli

30 Pediatric Infections Present as pyelonephritis due to E. coli Symptoms include urinary frequency with urgency, dysuria, incontinence, or incomplete bladder emptying Potential for fungal infection if immunosuppressed and catheterized Fungal infections are more difficult to diagnose, but can be present in premature infants or those with poor nutrition Evaluation Children <2 years with fever should be evaluated for a UTI and bacteremia Children >2 years more likely to present with cystitis especially if constipated or on antibiotic therapy

31 Evaluation of the Pediatric Patient Collection is based on urinary control of the child Sterile suprapubic aspiration Catheterization not the best, high contamination Clean catch midstream Use of sterile pediatric collection bag not recommended Pyruria and bacteriuria present on urinalysis 50,000 cfu/ml present on culture

32 References American Urology Association as accessed online through Nancy Brunzel (2013). Fundamentals of urine and body fluid analysis, 3 rd Ed. Elsevier Press. Charles Kodner. and Emily Thomas-Gupton (2010). Recurrent Urinary Tract Infections in Women: Diagnosis and Management. Am Fam Physicians. Sep 15;82(6): ). Clinical Laboratory Standards Institute(2009). GP16-A3 Urinalysis; Approved Guideline Third Edition. Donna Fisher and Russell Steele, et al. (2015). Pediatric urinary tract infection as accessed through Kim Gibson and Joseph Toscano (2012). Urinary Tract Infection Update. American Journal of Clinical Medicine. Vol 9, No. 2. John Brusch and Michael Stuart Bronze, et al. (2015) Urinary tract infection in males. As accessed through John Brusch and Michael Stuart Bronze, et al. (2015) Cystitis in females. As accessed through John Delanghe and Marijn Speeckaert (2014). Preanaltyical requiremnets of urinalysis. Biochemia Medica, 24(1): Juan Kattan and Steve Gordon (2013). Acute uncomplicated urinary tract infections. As accessed online through Connie Mahon, Donald Lehman, Geoger Manuselis (2011). Textbook of diagnostic microbiology, 4 th Ed. Saunders Elsevier Press. M. Miller. and A. Simundic (2013). Low level of adherence to instructions for a 24 hour urine collection among hospitalized patients. Biochemia Medica, 23(3): Niall F. Davis and Hugh D. Flood (2011). The Pathogenesis of Urinary Tract Infections, Clinical Management of Complicated Urinary Tract Infection, as accessed through Sysmex UF-1000i. A new generation automated urine particle analyzer.

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