Various physiologic and benign pathologic processes can lead to an elevation of serum PSA level. These factors include nonmalignant diseases of prostate, such as benign prostatic hyperplasia, acute and subacute prostatitis, prostatic ischemia, and infarction of the prostate.
Urinary retention and ejaculation can also lead to increased PSA levels in the absence of prostatic diseases. In addition, physical manipulation of the prostate, such as prostatic massages, cystoscopy, or in rare cases, digital rectal examination, can also increase serum PSA levels (Greene et al, 2009; Hermann et al, 2004; Tchetgen et al, 1997; Lee et al, 2012;
Kratz et al, 2003; Ulman et al, 2004).
There also have been many studies about the biologic variation of serum PSA levels (Komatsu et al, 1996; Roehrborn et al, 1996; Nixon et al, 1997). More recent survey of published 27 studies suggested that a single measurement of serum PSA level may not be sufficiently precise for screening and diagnosis of prostate cancer, because the mean biological variation of PSA was 20% in the range 0.1-20 ng/ml for men over 50 years (Sölétormos et al, 2005).
With regard to the daily variability of serum PSA level, Mermall et al. (Mermall et al, 1995) reported a circadian variation of serum PSA with a nadir value in the early morning and a peak value at midafternoon; On the contrary, Tekin et al. (Tekin et al, 2001) demonstrated a diurnal rhythm of PSA with a peak value at 8 am with a gradual decline throughout the day until midnight. However, many other studies reported that the variations of serum PSA values during a 24-hour period were random without any diurnal or circadian pattern (Dejter et al, 1988; Mannini et al, 1988, Akimoto et al, 1994; Glenski et al, 1992).
Therefore, it is unlikely that there is an optimal time point during a 24-hour period to determine PSA, and the blood samples for serum PSA values can be drawn from patients any time of day (Sölétormos et al, 2005; Mermall et al, 1995; Tekin et al, 2001; Dejter et al, 1988;
Mannini et al, 1988, Akimoto et al, 1994; Glenski et al, 1992; Klein et al, 1997)
Also, there have been a few reports about the discrepancy between outpatient and inpatient serum PSA values in the same man. Stamey et al. (Stamey et al, 1987) reported that the serum PSA levels checked 24 hours after admission decreased by a mean of 18% with a
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maximum of 50% when compared with the prior preadmission levels. This may be due to the lack of activity associated with bed rest during hospitalization, and physical exertion at ambulatory status would cause an increase in serum PSA values. Leventhal et al. (Leventhal et al, 1993) confirmed the findings of Stamey et al. (Stamey et al, 1987) by showing a significant difference between outpatient values and inpatient values checked after a minimum of 24 hours at bed rest after admission; yet found that stressful exercise of cardiac stress testing during hospitalization had no effect on serum PSA values. Tekin et al. (Tekin et al, 2001) also found that the serum PSA levels checked 72 hours after hospitalization significantly decreased by a median of 12% compared to the values obtained immediately before admission. Although the reasons for this decrease in the serum PSA level are uncertain, it is still probable that the lack of activity compared to the preadmission ambulatory status could contribute to the decrease in serum PSA level, because blood samples were obtained 24-72 hours after admission in the above 3 studies.
The effect of exercises on the serum PSA level is controversial. While exercises such as bicycle riding increased the serum PSA levels in some reports (Rana et al, 1994; Oremek et al, 1996), exercises such as bicycle riding or high-altitude trekking did not affect the serum PSA levels in the others (Safford et al, 1996; Verratti et al, 2007). In the most recent study by Loprinzi and Kohli (Loprinzi et al, 2013), participants were 16% more likely to have an elevated serum PSA level for every 1-hour increase in sedentary behavior, and were 18% less likely to have an elevated serum PSA level for every 1-hour increase in light physical activity.
Therefore, they suggested that the individuals who engage in more sedentary behavior and lower levels of light physical activity have higher serum PSA values.
In the current study, we obtained the blood samples for the IPsPSA testing just after admission, and revealed that the IPsPSA was decreased compared with the preadmission level. Therefore, the effects of resting and sedentary behavior did not seem to affect the results. The diurnal variation of serum PSA values also might not affect the results.
Therefore, the reasons for the decrease in serum PSA level after hospitalization is still not certain. The reasons for the decrease in the IPsPSA levels compared to OPsPSA levels, but without statistical significance, in cases with ages of 20-39 years and PSA <4 ng/ml might be due to the small sample size of these subgroups compared to the other subgroups.
In this study, we excluded the patients who did not have OPsPSA measured in our hospital
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to eliminate the effects of assay variability due to the different methods of PSA measurements (Slev et al, 2008; Brawer et al, 1995). We also excluded the patients with the interval of more than 1 month between OPsPSA and IPsPSA to minimize the possible effect of the biologic variation of serum PSA levels. We also excluded the patients who had pathologic diagnosis of prostate cancer, because the serum PSA level might be increased during the time interval between the OPsPSA and IPsPSA.
This study had several limitations. This study was conducted in a single center. It was retrospective in nature and the size of the study population was small. The factor of recent ejaculation, which can affect the serum PSA level, was not analyzed in this study.
Nevertheless, we believe that the IPsPSA levels were decreased compared to OPsPSA levels, thus the hospitalization itself decreases the serum PSA levels. Therefore, the serum PSA values should be checked on an OPD basis for the serial monitoring of PSA levels. The larger prospective multicenter study will be needed to confirm these results.
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