Açlık-tokluk PSA değerleri: Ölçümler açlık kanında mı yapılmalı?

Abstract

Prostat kanserinin erken tanısında PSA yaygın olarak kullanılan bir tümör belirleyicisidir. Bununla birlikte serum PSA seviyesinin bir çok faktörden etkilenmesi ve prostatın kanser dışında diğer patolojilerinde de serum PSA seviyesinin değişmesi PSA'nın değerini sınırlamaktadır. Bu çalışmada serum PSA seviyesinin açlık-tokluk ile olan ilişkisi araştırıldı.Serum PSA seviyesine açlık ve tokluğun olası etkisini araştırmak amacıyla aynı öğünü alan sağlıklı 33 kişi çalışmaya alındı. Her kişiden yemekten bir saat önce, bir saat sonra ve ikinci saatte kan örnekleri alındı. Serum PSA değeri elektrokemiluminesens yöntemiyle bakıldı. İstatistiksel analizde Paired-t testi ve Pearson korelasyon katsayısı kullanıldı. Ortalama yaş 42±17.5 idi. Ortalama açlık, tokluk 1. saat ve tokluk 2. saat serum PSA değerleri sırasıyla 0.70±0.69, 0.74±0.75 ve 0.65±0.57 idi. Açlık ortalama serum PSA değeri ile yemekten sonraki gerek 1. saat ve gerek 2. saat ortalama serum PSA değerleri arasında istatistiksel anlamlı fark saptanmadı (p>0.05). Ancak yemek sonrası 1. ve 2. saat kan örneklerinde serum PSA'daki değişim istatistiksel olarak anlamlı idi (p=0.029). Bu çalışmada yemek sonrası 1. saat PSA düzeylerinde yükselme ve 2. saat düzeylerinde de anlamlı bir düşüş olduğu gösterilmiştir. Bu değişikliklerin sınır PSA değeri olan olgularda invaziv bir girişime karar vermeyi etkileyebileceği düşünülerek kan örneği elde edilmesinde hastanın aç/tok oluşu göz önüne alınmalıdır.

Introduction: Prostate specific antigen (PSA) is the commonly used tumor marker in the early diagnosis of prostate cancer. Although it is highly specific for prostate, its specifity is low for prostate cancer. Since it is affected by many factors other than cancer such as diurnal variations of the secretion, existing of infections or inflammations in the prostatic tissue, volume of prostate, digital rectal examination, ejaculation or rectal manipulations and surgery of the prostate, the value of serum PSA level is limited. Serum insulin level increases and reaches maximum level at first hour due to increased glucose level after meal. Thereafter the level of serum insulin values return to its normal level at approximately two hours after meal. On the other hand, insulin suppresses the production of sex hormone binding protein in liver cells. Therefore, it is logic to investigate PSA levels due to metabolic and hormonal changes after meal. We investigated changes of PSA level after meal in this prospective study. Materials and Methods: Thirty-three healthy cases were included in this study to determine changes of serum PSA levels pre and post-meal manner. All patients were given same regular diet comprised of 700 calories (50-55% carbohydrates, 25-30% lipids and 20% proteins). Blood samples were taken an hour before meal (PSA-0), and one (PSA-1) and two (PSA-2) hours after meal. Serum PSA levels were determined by chemiluminescence method. Paired sample t test and Pearson correlation coefficient were used for statistical analysis. Results: The mean age of the patients was 42±17.5 (Range 20-80) years. The mean PSA level at one hour before meal, one and two hours after meal were 0.70±0.69 ngr/ml (PSA-0), 0.74±0.75 ngr/ml (PSA-1) and 0.65±0.57 ngr/ml, (PSA-2) respectively. There was no statistically significant difference between serum PSA-0 levels with PSA-1 (p=0.106) and PSA-2 (p=0.109) levels. However, there was a statistically significant difference between first hour and second hour after meal mean PSA levels (p=0.029). Conclusion: Serum PSA values may be affected not only from prostatic disturbances, but also the changes of its metabolism and levels of PSA binding proteins. Insulin, proinsulin, C-peptid and Zn secretion increase after meal. In contrast, glukagon, Cortisol, epinephrin, norepinephrin secretion decrease. These differences could also change the levels of detectable fractions of PSA temprorarily and may affect serum total PSA levels. The differences of serum PSA levels represent paralelisin with the changes in serum insulin levels after meal. In this study, mean PSA levels increased at first hour after meal and decreased at second hour after meal. These differences in PSA levels could affect the decision making for indication of prostate biopsy in patients with borderline PSA levels and it should be considered when the serum samples are taken whether patients are hungry or not. The determination of ideal serum PSA sampling time would be important in order to prevent false negative or positive serum PSA results. In this way, clinicians would decide not to do invasive procedures especially in patients with borderline serum PSA levels.