Accuracy and safety of a novel aqueous humor collector versus 29 G insulin syringe for anterior chamber paracentesis and aqueous humor collection: A multicenter randomized clinical trial.

To the Editor: Anterior chamber (AC) paracentesis is a commonly performed procedure to lower intraocular pressure (IOP), and to sample aqueous humor (AH) for clinical and research purposes. As suggested by an international collaboration team, an immediately performed AC paracentesis before an intravitreal injection can also prevent post-injection IOP spike.[1] While IOP could immediately be reduced by AC paracentesis, the procedure of obtaining an AH sample (liquid biopsy) is more complicated. Several methods have been developed to facilitate AH collection and transfer,[2–7] among which a vacuum-based AH collector (SnovoDAHC I-50, Sightnovo Medical Technology Co., Beijing, China) has better performance than the commonly used insulin syringe in accurate sampling of about 50 µL AH in rabbits by one hand.[7] The current clinical trial aimed to evaluate the performance and safety of this product in human subjects. This study was a prospective, two-center, randomized, parallel controlled superiority clinical trial. Adhered to the tenets of the Declaration of Helsinki, this trial was approved by Institutional Review Boards of Peking Union Medical College Hospital (center 1, No. HS2020040) and Union Hospital, Tongji Medical College, Huazhong University of Science and Technology (center 2, No. 20200380). When the alpha and beta were set at 0.05 (two-sided) and 0.2 (80% power) respectively with an allocation ratio of 1:1 and an estimated drop-out rate of 20%, at least 108 participants were needed to reveal a statistically significant difference between groups. To ensure sufficient data, this study planned to enroll 120 participants. Patients with acute ocular hypertension, or scheduled for diagnostic AH sampling or intravitreal injection were potential candidates for screening tests. A total of 135 patients were screened and 15 patients were excluded after the screening phase. The detailed exclusion criteria are presented in Supplementary Appendix 1, https://links.lww.com/CM9/B690 and the process of participant disposition is shown in Supplementary Figure 1, https://links.lww.com/CM9/B690. Written informed consents were obtained from all enrolled participants. For all included participants, baseline documentation including coagulation tests, anterior segment photography, IOP, AC depth and axial length (AL) measurements were completed before the operation. AC paracentesis with AH collection was arranged immediately for patients with ocular hypertension. Baseline IOP was remeasured if AC paracentesis was not performed within 4 hours after the last measurement. Besides, IOP measurement, anterior segment examination with photography and AC depth measurement were performed between 30 minutes and 2 hours after the procedure, and reevaluated in the follow-up visit 28 ±7 days after the procedure (D28 follow-up). Refer to Supplementary Table 1, https://links.lww.com/CM9/B690 for detailed descriptions of the examinations/measurements. AC paracentesis and AH collection were performed with a SnovoDAHC I-50 collector in the collector group, or with a 29 G insulin syringe (BD Ultrafine Insulin Syringe 1mL 29 G×1/2″ U-40, Becton, Dickinson and Company, New Jersey, USA, #328421) in the syringe group [Figure 1]. In the collector group, AH was collected in a one-handed manner as previously described at the slit lamp in a consulting room [Supplementary Video 1, https://links.lww.com/CM9/B691],[8] or with the patient in supine position in an operating/treatment room [Supplementary Video 2, https://links.lww.com/CM9/B692]. In the syringe group, AH could either be drawn into the syringe by pulling the plunger, or be collected by a plunger-off syringe,[2] and then transferred into a 0.5mL micro-centrifuge tube.Figure 1: The disposable aqueous humor collector(SnovoDAHC I-50; shown above) and the control device ultrafine insulin syringe 1mL 29 G×1/2" U-40(BD Ultrafine insulin syringe; shown below).The target volume in the syringe group was intentionally set at 50 µL. User experience of the medical device, intra-operative complications, and device malfunctions if there was any, were recorded immediately after the procedure. The primary outcome of this study was success rate of accurate AH collection, which was defined as collection of 40 to 60 µL AH. Weight of the AH collected was calculated by subtracting the net weight of the collection tube/micro-centrifuge tube from its loaded weight. The volume of AH (µL) collected by the AH collector/syringe was calculated by dividing the weight gain of the collection tube/micro-centrifuge tube (mg) in the procedure by its approximate density of 1.0 mg/mL. A 5-dimensional rating scale (structural and material design, ease of use, safety, efficiency, and preciseness) was designed to evaluate the user experience of the operator for the device. Each dimension was scored on a 0–2 scale which resulted in a total score of 0–10. Statistical Analysis System (SAS) version 9.1.3 (SAS Institute, Cary, NC, USA) was used to conduct statistical analyses. We analyzed the demographic characteristics, laterality, lens condition, reason for AC paracentesis of the study eyes between the collector and the syringe groups and found no significant difference between the two groups [Supplementary Table 2, https://links.lww.com/CM9/B690]. Among the three baseline ocular measurements (IOP, central AC depth and AL) of the study eyes, central AC depth in the syringe group was statistically significantly deeper than that in the collector group (P = 0.017). This was at least partially due to the larger proportion of pseudophakic eyes included in the syringe group than in the collector group (21.4% [12/56] vs. 9.1% [5/55]) because exclusion of the pseudophakic eyes led to insignificant statistical results between the groups (P = 0.102). None of the measurements was statistically different in the control eyes between the groups. The volumes of AH obtained in the collector and syringe groups were 51.63 ± 3.23 µL and 49.84 ± 15.33 µL respectively in center 1, 49.09 ± 4.71 µL and 51.60 ± 11.77 µL respectively in center 2, and 50.62 ± 4.05 µL and 50.50 ± 14.01 µL respectively in two centers combined [Supplementary Figure 2, https://links.lww.com/CM9/B690]. The success rates of accurate AH collection in the collector and the syringe groups were 100% (33/33) and 51.43% (18/35) respectively in center 1, 100% (22/22) and 57.14% (12/21) respectively in center 2, and 100% (55/55) and 53.57% (30/56) respectively in two centers combined. The success rates of the collector group were statistically significantly higher than that of the syringe group in both centers and in combination (Z = –4.581, P <0.0001 in center 1; Z = 3.396, P = 0.0007 in center 2; Z = –5.745, P <0.0001 in combination). The difference of success rate between the two groups was 46.43%. And the asymptotic and exact two-sided 95% confidence intervals for the difference in success rate of accurate AH collection between the collector group and the syringe groups were [0.334, 0.595] and [0.330, 0.604], respectively. The lower limit of the two-sided 95% confidence intervals was greater than the pre-specified superiority margin (0.15), which indicated that the collector group had superiority in primary efficiency. Among the 5 subjective rating dimensions, the collector group had significantly higher median rating scores than the syringe group in "ease of use", "efficiency", and "preciseness", and the two groups had comparable rating scores in "structural and material design" and "safety". The collector group had significantly higher median total rating score [Supplementary Table 3, https://links.lww.com/CM9/B690]. AC paracentesis with AH collection was performed safely in all study eyes. Neither device deficiency nor serious adverse event (SAE) was reported during any procedure. A total of 14 adverse events (AEs) were documented, of which each group and each center reported 7 AEs; in the collector group, 5 mild AEs (5/7) and 2 moderate AEs (2/7) were documented, while in the syringe group, 4 mild AEs (4/7), 2 moderate AEs (2/7) and 1 severe AE (1/7) was reported. The difference of AE incidence between the two groups was not statistically significant (P = 0.971). Of all 13 ocular AEs, 12 recovered or resolved completely during follow- up except for the incident of sustained ocular hypertension. Detailed description of the AEs is shown in Supplementary Table 4, https://links.lww.com/CM9/B690. Overall, as compared with previous syringe- and pipet- based devices,[2–7] the novel aqueous humor collector is advantageous in the following aspects. With precisely preset vacuum in the collector tube, this device enables accurate sampling of 40–60 µL AH, which greatly reduce the risk of inadequate sampling and over decompression of AC. The procedure can be easily performed in a one-handed manner in different clinical scenarios with the patient sitting at the slit lamp or in supine position. Sterileness of AH is maximally preserved during the whole sampling process, which is important for some diagnostic tests. The collection tube itself is a micro-centrifuge tube suited for low-temperature storage, centrifugation and pipetting of AH sample, therefore, sample transfer is not needed after the paracentesis. With all these features, the novel aqueous humor collector had significantly higher accurate sampling rate and subjective rating scores than the control device in this study, is therefore a better choice for AH collection. Conflicts of interest None.