VIMS Journal: July 2017

Original Article

A Pilot Study of Prevalence of Raised Prostate Specific Antigen Levels in Elderly Men with Low Back Pain

Dr. D. K. Jha, Dr. S. Ghosh, Dr. S. Mahapatra

Abstract :
Prostate cancer patients frequently present with back pain due to spinal metastasis.
PSA levels are not routinely recommended in asymptomatic males but PSA and digital rectal examination in elderly males with low back pain is often useful for diagnosis of prostate cancer.
In this study, we find the prevalence of raised PSAamong elderly men presenting with back pain.

Keywords :
PSA, prostate specific antigen, low back pain, spinal metastasis, prevalence

Introduction:Low back pain is a common complaint among primary care outpatients. The prevalence of LBP in Indian population has been found to vary between 6.2% (in general population) to 92% (in construction workers)[1]; estimates of the cumulative lifetime prevalence range from 13.8% for persistent painto as high as 80% for any episode of pain[2]. In the majority of cases of back pain, a specific diagnosis is not made, and patients usually recover within a few weeks of the onset of symptoms.
An important goal of diagnostic testing is to identify the serious systemic causes of back pain, such as malignancy, infection, and inflammatory disease. Although malignancy is the most common of these systemic problems, the prevalence of spinal malignant neoplasms (usually metastatic disease) among primary care patients with low back pain is less than 1%.[3] An important goal of early diagnosis and treatment of spinal metastasis is to prevent complications, which may include pain, pathologic fracture, weakness, sensory loss, paralysis, and bowel or bladder dysfunction. Among patients who develop epidural spinal cord compression, those who are diagnosed early, while still able to ambulate, are the most likely to remain ambulatory following treatment.[4] The ideal diagnostic strategy would detect the few cases of cancer among primary care patients with low back pain, while minimizing unnecessary diagnostic testing.
Diagnosis of prostate cancer may be incidental or contribute to the cause of mechanical back pain. With such high mortality associated with metastasis, early detection is essential for appropriate medical management. Orthopaedic surgeons are often consulted for back pain of mechanical origin and are in a position to detect conditions in which serious organic pathology may contribute to, or mimic benign musculo skeletal back pain.
Prostate-specific antigen (PSA) is a widely used specific tumour marker for prostate cancer. The serum prostate-specific antigen (PSA) level is highly predictive of bone metastasis. If the serum PSA level is above 4 ng/ml, the positive predictive value is 30 percent.[5] PSA is a 33-kd glycoprotein consisting of 240 amino acids. It is a serine protease secreted by the ducts of the prostate gland into semen, where it causes lysis of seminal coagulum. PSA in blood occurs in three forms: free PSA, PSA complexed with 1-antichymotrypsin, and PSA complexed with 2-macroglobulin. The serum PSA test measures the level of free and bound PSA in the blood. Normally, the level of PSA detected in the blood is between 0.0 and 4.0 ng/ml.Most men who have been diagnosed with prostate cancer have a PSA level greater than 4.0ng/ml.[6] The test has a reported sensitivity (the probability that a person having the disease will be correctly identified by a clinical test) of up to 80% in detecting prostate cancer but it lacks specificity (the probability that a person not having the disease will be correctly identified by a clinical test). The positive predictive values of PSA screening studies are reported to be between 28ñ35%, which means only one third of the men with elevated PSA (>4ng/ml) will be found to have prostate cancer on biopsy and two thirds will not.[7] Other non-malignant conditions that increase PSA levels include: benign prostatic hyperplasia, urinary tract infections, prostatitis or any other condition or diagnostic test that might irritate the gland. Thus, false positive results are common.[6]
About 2/3rd of the malignant tumour cases develop metastasis, and the incidence of malignant tumour is consecutively increasing every year. The skeletal system is the third most common site of metastasis, and the spine is the most common site of metastasis. Prostate cancer and bronchial cancer are most common in male to cause spinal metastasis in males.[8]

Aims and objectives :
To find out the prevalence of PSA value greater than 4.0 ng/ml in male patients of >50 yr. age and presenting with >3 m duration of low back pain.
To find a parameter for differentiating low back pain from serious systemic cause so that prompt referral can be done.
To develop PSA as a screening tool for occult prostate cancer with spinal metastasis.

Materials and methods :We included 29 males presenting to orthopaedic OPD of our hospital during period of 1st February 16 to 31st January 17 (1 year). They were of =50 years age and had low back pain >3m duration not relieved by conservative management. We excluded patients with radiological evidence of spondylolisthesis, degenerative disc disorder. After proper informed consent, we obtained the serum PSA along with routine blood examination of these patients.
PSA was measured by fully automated regular COBAS CORE PSA Electro Immunoassay (ROCHE Inc.)
A level of 4.0 ng/ml was taken as upper limit of normal.
The period prevalence was calculated as= no. of patients with raised PSA/ total no. of patients screened x 100.
Patients with PSA=4 ng/ml were referred to urologist for further evaluation.

Results:
The PSA levels of 15 patients was found to be more than 4 ng/ml out of the 29 patients screened. The period prevalence was 51.7 per 100 persons.

Prevalence of PSA>4 ng/ml
Author Study Population Prevalence of PSA>4 ng/ml in ≥50 years age
O. Erhabor et al9 Healthy men of African descent 33.3%
T. Malati and G. Rajani Kumari10 Healthy South Indian men 6.2%
Our study ≥ 50 yr. men with low back pain > 3m duration 51.7%

Discussion : In our study, we found that the prevalence of raised PSA (>4 ng/ml) was 51.7 per 100 persons which was higher than the prevalence found in other studies done in general population.

Conclusions:
Routine use of serum PSA in patients complaining of unremitting chronic low back pain who are at high risk for prostate cancer is recommended as it is cost effective, less invasive and has diagnostic efficacy. High prevalance rate of raised PSA in older age group makes the test not very specific but very high levels certainly helps to detect some occult cases of prostatic CA. Routine use of PSA test in persistent Low Back Pain cases is recommended and is useful.

References
  1. Supreet Bindra, Sinha A.G.K and Benjamin A.I. Epidemiology of low back pain in Indian population: a review. International Journal of Basic and Applied Medical Sciences 2015 Vol. 5 (1) January-April, pp. 166-179.

  2. Deyo RA, Tsui-Wu YJ.Descriptive epidemiology of low-back pain and its related medical care in the United States. Spine. 1987 Apr; 12(3):264-8.

  3. Deyo RA, Diehl AK Cancer as a cause of back pain: frequency, clinical presentation, and diagnostic strategies. J Gen Intern Med. 1988 May-Jun; 3(3):230-8.

  4. Sˉrensen S, Bˉrgesen SE, Rohde K, Rasmusson B, Bach F, Bˉge-Rasmussen T, Stjernholm P, Larsen BH, Agerlin N, Gjerris F Metastatic epidural spinal cord compression. Results of treatment and survival.Cancer. 1990 Apr 1; 65(7):1502-8.

  5. Wolff JM, Bares R, Jung PK, Buell U, Jakse G. Prostatespecific antigen as a marker of bone metastasis in patients with prostate cancer. Urol Int.1996; 56:169-73

  6. Catalona WJ1, Smith DS, Ratliff TL, Dodds KM, Coplen DE, Yuan JJ, Petros JA, Andriole GL.Measurement of prostate-specific antigen in serum as a screening test for prostate cancer.N Engl J Med. 1991 Apr 25;324(17):1156-61.

  7. Oesterling JE. Prostate specific antigen: a critical assessment of the most useful tumor marker for adenocarcinoma of the prostate. J Urol. 1991 May; 145(5):907-23

  8. Chong-Suh Lee corresponding author and Chul-Hee JungAsian. Metastatic Spinal Tumor Spine J. 2012 Mar; 6(1): 71-87.

  9. O. Erhabor et al. PSA screening among apparently healthy men of African descent. International Blood Research and Reviews 2014 2 (1) : 37-47.

  10. T. Malati and G. Rajani Kumari. Racial and ethnic variation of PSA in global population: age specific reference intervals for serum prostate specific antigen in healthy south Indian males. Indian journal of clinical biochemistry, 2004, 19(1) 132-137.

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