Division of Clinical Laboratories, Bikur Cholim Hosptial, 5 Strauss Street, Jerusalem 91004, Israel. e-mail: MAlmagor@bikurholim.org.il
Dear Sir,
We thank Dr Sacks et al. for their interest in our article (Almagor et al., 2004) and appreciate the opportunity to address their comments.
As described in the Materials and methods section in our paper, C-reactive protein (CRP) values <5 mg/l were considered normal. Sacks et al. misinterpreted these values as the lower detection limits of the test. In fact, the lowest detection level was 0.5 mg/l. Because CRP has a relatively wide range, the measurement of CRP ratios overcomes range differences between individuals.
We certainly agree with Sacks et al. that exclusion of patients with incomplete sets of CRP analyses reduced the study population. However, this did not introduce any bias since failure to obtain blood specimen was randomly distributed, resulting in omission of both pregnant and non-pregnant women.
The suggestion that CRP levels are positively correlated with the number of oocytes seemed interesting. In our study, the mean number of oocytes retrieved was 13.3 ± 7.4 in the pregnancy group and 13.9 ± 7.0 in the non-pregnant women. CRP levels on the day of oocyte retrieval were 9.4 ± 11.9 and 5.2 ± 7.6 respectively. It should be noted that we obtained blood for CRP before oocyte collection was started (Materials and methods section). Thus, the explanation offered by Sacks et al. does not fit our data.
Their claim, that in IVF pregnancies CRP levels increase on day 14 after oocyte collection, is in no contradiction to our findings. Since we evaluated CRP only up to day 12, further elevation of CRP is plausible. However, it seems obvious that hCG test on day 14 cannot be replaced by CRP measurement.
References
Almagor M, Hazav A and Yaffe H (2004) The levels of C-reactive protein in women treated by IVF. Hum Reprod 19,104106.
Submitted on February 9, 2004; accepted on February 18, 2004.