Urinalysis and dipstick interpretation

What it is

The dipstick urinalysis is a test whose result is a first step and not a diagnosis. A random dipstick urinalysis may show 2+ protein while a repeat dipstick in the office shows 1+ protein and is otherwise normal, so the result has to be confirmed before it is acted on.

Causes and risk

Bacteria in the urine are common with age and do not on their own mean infection. In women age 70 and older the incidence of asymptomatic bacteriuria is 16% to 18%, and in chronically incontinent and disabled older adults rates may reach 43%.

Whether a positive dipstick belongs to an uncomplicated infection depends on who has it. An uncomplicated UTI occurs in healthy asymptomatic non-pregnant women, with no history of urinary tract abnormalities, and not posted for any urological procedure. Everything outside that is complicated, which means an increased chance of treatment failure. The risk factors are grouped in three. Patient characteristics: male sex, postmenopausal, pregnant, presence of hospital-acquired urinary tract infection, and symptoms present for seven or more days before presentation. Urologic conditions: history of childhood or recurrent urinary tract infections, indwelling catheter, neurogenic bladder, polycystic kidney disease, recent urologic instrumentation, renal transplant, urolithiasis, urologic obstruction, and urologic stents. Medical conditions: diabetes mellitus and immunocompromised status. Some experts count three of these groups as uncomplicated even so: healthy postmenopausal women, patients with well-controlled diabetes, and patients with recurrent cystitis that responds to treatment.

Three cases are worth measuring against that definition: a 35 year old pregnant woman with occasional dysuria whose dipstick is positive for leucocytes with a negative nitrite; an otherwise healthy 40 year old man at a general checkup, asymptomatic, whose dipstick is positive for leucocytes and nitrite; and an asymptomatic 75 year old man with HTN, positive for nitrites, who is posted for TURP next week after evaluation for BPH. By the definition above none of the three is an uncomplicated UTI, since pregnancy, male sex and a urological procedure to come each fall outside it. All three are to be treated, and that holds even for the two of them who are asymptomatic.