INVESTIGATION OF URINARY SYMPTOMS Blood tests

INVESTIGATION OF URINARY SYMPTOMS Blood tests

Blood counts and chemistry Initial blood tests in suspected urological pathologies include a full blood count, urea, creatinine and electrolytes. Creatinine, a surrogate marker for renal function (glomerular filtration), is an end product of muscle catabolism and may be unchanged despite a wide variation in estimated glomerular filtration rate (eGFR). eGFR is recommended as the optimal method of reporting renal function in many countries. Patients with calculous disease routinely have serum calcium, uric acid and parathyroid hormone levels checked to rule out a metabolic predisposition to stone formation. Serum alkaline phosphatase may be elevated in patients with bone metastases due to a ur ological malignancy and is commonly seen in men with disseminated prostate cancer. Summary box 81.4 Biochemical assessment of renal function /uni25CF /uni25CF /uni25CF

eGFR is increasingly reported along with urea and creatinine as it is more informative of true renal function With both kidneys functioning normally, an individual has approximately six times the renal function needed to remain off dialysis Serum creatinine will remain normal with unilateral renal pathology but a normally functioning contralateral kidney

Serum tumour markers are utilised in patients with prostate and testicular cancer. Currently no serum tumour markers exist in routine clinical practice for renal or bladder cancer. Prostate-specific antigen PSA is a glycoprotein produced by prostatic epithelial cells. Altered architecture of the prostate in conditions such as BPH, prostatitis and prostate cancer allows PSA to enter the blood stream and be detected by a blood test. The commonly used PSA assays measure the total amount of PSA (tPSA). PSA levels can be influenced by certain drugs, most notably 5 α -reductase inhibitors used to treat men with LUTS, but also by aspirin, statins and thiazide diuretics. The PSA test can be significantly influenced by a recent UTI and the true PSA level only returns to baseline 6 weeks after eradication of an infection. Summary box 81.5 Prostate-specific antigen /uni25CF /uni25CF /uni25CF /uni25CF α PSA values in a population of men form a continuum with no clear abnormal threshold. The value of PSA that triggers a biopsy is variable and is influenced by age, ethnicity , family history and findings on DRE. The benefits of screening asymptomatic men for prostate cancer using PSA testing are controversial and a large UK-based clinical study (ProtecT trial) found that at a median of 10 years very few patients died of prostate cancer irrespective of treatment or surveillance. At present, PSA-based screening for prostate cancer is not routinely performed in the UK but men interested in having a PSA test can request this from their family practitioners. A similar practice is followed in many countries. Risk prediction models have been developed in recent years to assist clinicians and patients in predicting prostate cancer diagnosis, stage and prognosis. A number of these risk assessment tools are available online as a decision aid for an individual man to ev aluate his own risk of prostate cancer. These include the Prostate Cancer Prevention Trial (PCPT) Risk Calculator and the European Randomized Study of Screening for Prostate Cancer (ERSPC) Risk Calculator. For men newly diagnosed with prostate cancer, PSA assists with risk (of disease progression) stratification. It is also a useful marker of response to treatment and of disease recurrence after treatment. Franz Ziehl , 1859–1926, German bacteriologist and a professor in Lübeck, Germany . Friedrich Carl Adolf Neelsen , 1854–1898, German pathologist and professor at the Institute of Pathology , University of Rostock, Germany . kinetics Since PSA may be elevated in non-malignant conditions, PSA derivatives/kinetics have been used to improve the specificity of testing. Some of the derivatives include free PSA (fPSA), complexed PSA (cPSA) and free/total PSA ratio (f/tPSA). Since BPH tissue within the prostate also contributes to tPSA, PSA density (PSAD) factors in the volume of the prostate by - dividing tPSA by prostate volume. A high PSAD increases the likelihood that the elevated PSA is due to malignancy and not due to the large gland alone. PSA kinetics involve measurement of the rate of change of various forms of PSA based on the premise that a rapid increase or change may be more predictive of cancer. PSA velocity is the annual absolute increase in tPSA /uni00A0 and a value >0.75 ng/mL per year compared with baseline has been considered suspicious. PSA doubling time is the number of months it takes for a baseline PSA to double. Testis tumour markers Serum tumour markers routinely used in the management of men with suspected testicular cancer are alpha-fetoprotein ( α FP), beta-human chorionic gonadotropin ( β HCG) and lactate dehydrogenase (LDH). These markers sometimes provide insight into the likely diagnosis, histological subtype of germ cell tumour present, success of treatment and recur - rence. They also contribute to the stratification of patients with testicular cancer into prognostic categories using a classification devised by the International Germ Cell Cancer Collaborative Group.

Is not signi /f_i cantly altered by DRE Can be signi /f_i cantly altered by a UTI After an infective episode, takes 6 weeks to return to baseline values Is arti /f_i cially lowered, up to two times, in men taking 5 -reductase inhibitors ( /f_i nasteride, dutasteride)