Correlation between Serum Prostate Specific Antigen and Prostate Volume in Nigerian Men with Biopsy Proven Benign Prostatic Hyperplasia: (A prospective study)
E Udeh, N Dakum, O Amu, V Ramyl
benign prostatic hyperplasia, nigerian men, prostate specific antigen, prostate volume
E Udeh, N Dakum, O Amu, V Ramyl. Correlation between Serum Prostate Specific Antigen and Prostate Volume in Nigerian Men with Biopsy Proven Benign Prostatic Hyperplasia: (A prospective study). The Internet Journal of Urology. 2009 Volume 7 Number 2.
Objectives: We studied the correlation between serum prostate specific antigen and the volume of prostate in Nigerian men with biopsy proven benign prostatic hyperplasiaPatients/Material and Methods: A total of 120 men with biopsy proven stromoglandular hyperplasia were included in the study. We analyzed PSA and total prostate volume (TV) measured by transabdominal ultrasound. We used Pearson correlation coefficient and linear regression model to describe the relationship between variables. RESULTS: The mean age of patients recruited for the study was 65.6years. The mean total prostate volume recorded in the study was 72.79mls ±44.38mls and mean PSA was 12.44±15.49ng/ml. Serum PSA level significantly correlated with TV (P<0.05). The Pearson correlation between PSA and TV was 0.3365 while that between age and PSA was 0.026. Conclusions: In Nigerian men with biopsy proven BPH the volume of the prostate significantly correlated with serum PSA. There was no significant correlation between age and PSA.
Benign prostatic hyperplasia(BPH) is a common condition among men1 and surgery for this condition is the second most common major operation for medicare in aged men (after cataract surgery)2. It is a pathological process that contributes to, but is not the only cause of lower urinary tract symptoms in ageing men.
Estimation of prostate volume may be useful in a variety of clinical settings. It is generally accepted though, that there is a minimal direct correlation between prostate volume and symptoms of BPH3, 4. Measurement of prostate volume is valuable in medical treatment of BPH as well; for example large prostates (total prostate volume more than 40mls) may respond better with 5 alpha reductase inhibitors while there is good clinical effect on smaller prostates with alpha blockers 5, 6. Measurement of prostate volume though most accurate with trans- rectal ultrasound (TRUS); results from measurements done by transabdominal ultrasound correlate well with that of TRUS 7.
Additionally, prostate volume can help in the interpretation of serum prostate specific antigen8. Serum PSA has been shown to correlate with prostate volume among white men without prostate cancer; thus nomograms for predicting prostate volume from serum PSA have been developed9. Moreover, some authorities suggest that PSA can be used to predict the therapeutic efficacy of treatment modalities for BPH on the grounds that PSA and prostate volume are correlated 10,11. Most data on the correlation between PSA and prostate volume have been obtained from western populations. Unfortunately, very few studies have been done among African men; more so, with the findings in Japanese men that they release more PSA per unit prostate tissue than white men12.It became imperative for us to carry out a prospective study to determine the correlation between PSA and prostate volume among Nigerian men.
Patients, Materials and Methods
This study was carried out in Jos University Teaching Hospital (JUTH), a tertiary health institution located in the heart of Jos the Plateau state capital. Plateau state is located in the central part of Northern Nigeria. This hospital receives referral for surgical and other health problems from Plateau state and neighboring states such as Nassarawa, Benue, Taraba, Adamawa, Bauchi, Gombe and Kaduna.
A total of 120 patients who were pathologically diagnosed with BPH by transrectal trucut biopsy specimen of the prostate at the outpatient clinic of Jos University Teaching Hospital from 2006 to2008 were included in the study. The reasons for biopsy were increased PSA (>4ng/ml) or abnormal digital rectal examination. Those with biopsy evidence of prostate cancer, prostatitis, prostatic intraepithelial neoplasia or atypical small acinar proliferation detected at any point during follow up were excluded from the study. We also excluded those who have received any form of medical, minimally, invasive or open surgical treatments.
The total prostate volume was measured by a consultant radiologist using a transabdominal ultrasound (GE Logics Expert 052128 model). The total prostate volume was calculated using the formula V=α×β×γ×π\6 (prolate ellipsoid formula). The PSA was determined by ELISA. Factors affecting PSA like trucut prostate biopsy, urinary tract infection, the use of finesteride, transurethral instrumentation and vigorous prostate digital examination were excluded.
As shown in Table 1, the mean age for the patients was 65.6±9.84 years. The maximum age of the patient enrolled for the study was 85 years. The maximum PSA value recorded in the study was 35ng/ml, though the mean PSA was 12.44±15.49 ng/ml. The maximum total prostate volume was 223.82mls. The correlation between age and PSA is 0.026 based on the Pearson’s correlation co efficient (P>0.05) as shown in figure 1
The correlation between total prostate volume and PSA is 0.3365 based on the Pearson’s correlation co efficient (P<0.05) as shown in figure 2.
The pathophysiology of clinical BPH has been attributed to bladder outlet obstruction secondary to prostatic enlargement13. Imaging modalities have been applied in estimating prostate size however; PSA is usually evaluated in patients with BPH as further evaluation to determine those that would benefit from prostate biopsy.
This study determined the correlation between serum PSA and prostate volume in Nigerian men with biopsy proven benign prostatic hyperplasia. The value of the mean prostate volume (72.79±44.38mls) in this study differed from a similar study on determination of prostate volume done by Ibinaye14 on Nigerian men (46.62±21.56mls). This difference may be attributed to numerical bias; more patients were enrolled in our study compared to theirs. However, when compared to prostate volume values obtained in Europe and America in which a range of 30.3±9.8 to 49.0±26.9 was obtained15, there was significant difference which could be explained by the late presentation of Africans to the clinic compared to the Caucasians. The mean PSA value compared to normal PSA range was elevated. This may be attributed to the mean prostate volume in this study which was high; since there is a correlation between PSA and prostate volume, the elevated mean PSA could be explained by this finding.
The study also showed that there was a statistically significant correlation between serum PSA and prostate volume in Nigerian men. This study agreed with the findings of Hochberg et al16 which pointed out that in patients with BPH proven by TRUS biopsy, PSA and prostate volume had a statistically significant correlation.
In addition, there was no significant correlation between age and PSA in our study. This result differs from that obtained among caucascians17. The difference may be attributed to a selection bias. The age of our patients was not evenly distributed across the age range; about 42% of the patients were aged between 70-85 years old. The uneven age distribution may have accounted for the difference in statistical analysis. There is a possibility that if we had enrolled more patients who were older the correlation between age and PSA might have become significant. This finding although differed from that noted by Sang Eun Lee et al18, agreed with what Yu-Lung Chang et al17 observed in their study of Taiwanese men.
In Nigerian men with biopsy proven BPH, the volume of the prostate significantly correlated with serum PSA. There was no significant correlation between age and PSA. These findings agreed with that of Taiwanese men.
Furthermore, interpretation of serum PSA result in Nigerian men should be done with caution, since generally, they present with large prostate volume which may influence the value of the PSA.. When in doubt, a PSA density should be done and if it is elevated, a prostate biopsy should be done