Abstract
Purpose: :
Platelets may act as a VEGF scavenger, limiting vascular proliferation. Our recent investigation of a single platelet measurement closely preceding laser suggests a relationship between thrombocytopenia and treatment-requiring retinopathy, particularly zone I disease. We sought to identify critical time periods with relation to either disease progression (weeks preceding laser) or ocular development (postmenstrual age) during which serum platelet deficit may be associated with subsequent development of treatment-requiring ROP.
Methods: :
Retrospective 1:1 matched case-control study. Cases (n=48) received ROP laser; controls (n=48) developed no or stage 1 ROP and were individually matched to cases for BW within 100 grams and GA within 1 week. Available platelet data from the 6 week period preceding laser (cases) or matched PMA (controls) were abstracted. For each week prior to laser and for each week PMA, means were compared for cases vs matched controls using paired t tests. Platelet levels are presented in units of 1,000/µL.
Results: :
With regards to disease progression, the greatest differences between platelet levels occurred four weeks preceding laser, but the differences did not attain statistical significance (weekly means 247 (SD 161) cases, 286 (159) controls, p=0.19). With regards to ocular development, weekly means were significantly lower for cases vs controls at PMA 30 weeks (173 (73) vs 310 (132), p=0.02), 31 weeks (184 (116) vs 303 (144), p=0.02), and 32 weeks (187 (121) vs 298 (142), p=0.02). This significant difference was not present for PMA weeks <30 and >32.
Conclusions: :
Our results suggest a critical window in ocular development, rather than disease progression, during which serum platelet deficit may be associated with the subsequent development of severe ROP. In our sample, this period falls between 30 and 32 weeks PMA. We cannot exclude the possibility that this window may be shifted to an earlier PMA when considering zone of disease in a larger sample. The roles of a threshold effect or cumulative platelet deficit during this time period also warrant further investigation.
Keywords: retinopathy of prematurity