Introduction
Methods
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1. What is the Doppler ultrasonography difference on the first postnatal day between neonates who developed NEC in comparison to those who did not?
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2. What is the Doppler ultrasonography difference at disease onset between neonates with and without NEC?
Search strategy
Eligibility criteria and study selection
Extraction of data from selected studies: components of data extraction form
Quality assessment
Analysis
Results
Study characteristics
Study | Year | Country | Design | Population | Groups | SMA Doppler indices | NEC definition | NEC time onset | Results |
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Coombs et al. [20] | 1992 | UK | Prospective case–control | 59 neonates: 27 term/preterm at-risk neonates (small for gestation age/low Apgar/exchange transfusion) 18 preterm controls 14 term controls | NEC: 3 (stages not provided) Controls: 56 | Peak systolic velocity | Not provided | 1, 7 and 21 days | Infants who developed NEC had a lower mean peak systolic velocity in comparison to non-NEC infants |
Guang et al. [12] | 2019 | China | Prospective cohort | 104 preterm neonates | NEC: 8 (2 stage I, 6 stage II) Controls: 96 | Peak systolic velocity, end-diastolic velocity, differential velocity, time average mean velocity, PI, resistive index | Bell’s staging criteria as modified by Kliegman and Walsh | Median 12 (7, 14) days | A higher peak systolic velocity 54.165 (42.423–68.463) versus 42.195 (34.278–48.553) cm/s; (P=0.027) and differential velocity 47.445 (35.010–60.043) versus 32.565 (27.545–39.073) cm/s; (P=0.02) were significantly related to the risk of NEC |
Khodair et al. [18] | 2014 | Egypt | Prospective cohort | 52 preterm neonates | NEC: 12 (5 stage I, 6 stage II, 1 stage III) Controls: 40 | Peak systolic velocity, end-diastolic velocity, PI, resistive index | Bell’s staging criteria as modified by Kliegman and Walsh | Not provided | Doppler indices of the SMA, peak systolic velocity (88.9 ± 17 cm/s and 53 ± 8.5 cm/s), end-diastolic velocity (18.75 ± 11.3 cm/s and 14.9 ± 5.6 cm/s), resistive index (0.78 ± 0.09 and 0.67 ± 0.1) and PI (1.53 ± 0.73 and 0.67 ± 0.15) were higher in NEC group than in controls, with statistically significant differences |
Louis et al. [22] | 2013 | India | Prospective case–control | 100 preterm intrauterine growth restriction/small for gestation age neonates 50 neonates with absent/reversed end-diastolic flow 50 controls with normal Doppler | In at-risk population: NEC: 16 (10 stage I, 6 stage II) In controls: NEC: 2 (1 stage I, 1 stage II) | End-diastolic velocity, resistive index | Bell’s staging criteria as modified by Kliegman and Walsh | Median 14 (3, 32) h | Resistive index on day 1 was higher in babies with absent/reversed end-diastolic flow [5.4 (3.3, 7.3)] who developed NEC compared to the control group [3.3 (1.7, 3.9)], (P=0.049). On further analysis, within absent/reversed end-diastolic flow group, end-diastolic velocity on day 1 (− 3.3 ± 4.1 vs. − 0.6 ± 5.1 cm/s; P=0.03) was lower in the neonates with NEC compared to those without NEC |
Study | Year | Country | Design | Population | Groups | SMA Doppler indices | NEC definition | NEC time onset | Results |
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Deeg et al. [11] | 1993 | Germany | Prospective case-control study | 28 neonates: 14 term/preterm neonates with NEC 14 term/preterm controls | NEC: 14 (stages not provided) Controls: 14 | Peak systolic velocity, end-diastolic velocity, time average mean velocity, resistive index | Not provided | Mean 15 ± 10 days | In the SMA of patients with NEC, the peak systolic velocity was 119.0 ± 57.7 cm/s, the end-diastolic velocity 10.2 ± 8.9 cm/s, and the time average mean velocity 28.0 ± 13.3 cm/s. The resistive index in patients with NEC was 0.88 ± 0.12. In controls, the following flow velocities were measured in the SMA: peak systolic velocity 68.4 ± 20.5 cm/s, end-diastolic velocity 11.8 ± 6.8 cm/s and time average mean velocity 13.0 ± 5.5 cm/s. The resistive index in the SMA of healthy infants was 0.84 ± 0.08. Statistical comparison with the healthy control group showed a significant increase in the peak systolic velocity and time average mean velocity, with a P<0.05 in patients with NEC |
Hashem et al. [21] | 2017 | Egypt | Prospective cohort study | 51 septic preterm neonates: 25 neonates with NEC 26 neonates with sepsis but no NEC | NEC: 25 (21 stage I, 3 stage II, 1 stage III) Controls: 26 | Peak systolic velocity, end-diastolic velocity, PI, resistive index | Bell’s staging criteria as modified by Kliegman and Walsh | Median 12 days | A statistically significant lower peak systolic velocity was found (P=0.001) and a lower end-diastolic velocity (P=0.001) in the SMA in the group with clinical signs of NEC in comparison with the group with no clinical signs of NEC |
Kempley et al. [13] | 1992 | UK | Prospective case–control study | 38 neonates: 19 preterm neonates with NEC 19 term/preterm controls | NEC: 19 (10 stage I, 9 stage II) Controls: 19 | Time average mean velocity, PI | British Association of Perinatal Medicine criteria | Mean 15 ± 13.4 days | Mean SMA velocity was significantly higher in the infants with confirmed NEC (36.5 cm/s) than in infants with suspected, unconfirmed disease (19.6 cm/s, P<0.05) |
Urboniene et al. [24] | 2015 | Lithuania | Prospective case-control study | 62 neonates: 29 term/preterm neonates with NEC 33 term/preterm controls | NEC: 29 (13 stage I, 12 stage II, 4 stage 3) Controls: 33 | Peak systolic velocity, time average mean velocity, PI, resistive index | Bell’s staging criteria as modified by Kliegman and Walsh | Not provided | The differences in the Doppler indices of SMA including peak systolic velocity, and time average mean velocity were not statistically significant between NEC and the control group. However, the values of resistive index and PI of SMA were significantly different between NEC and control groups (P<0.001) |
Case-control studies | |||||||||
Selection | Comparability | Outcome / Exposure | Quality score | ||||||
Adequate definition of cases | Representativeness of the cases | Selection of controls | Definition of controls | Comparability | Assessment of exposure | Assessment method | Non-response rate | ||
Coombs et al. [20] | * | * | - | * | * | * | * | - | Good |
Deeg et al. [11] | * | * | - | * | * | * | * | - | Good |
Kempley et al. [13] | * | * | - | * | * | * | * | - | Good |
Louis et al. [22] | * | * | - | * | ** | * | * | - | Good |
Urboniene et al. [24] | * | * | - | * | * | * | * | - | Good |
Cohort studies | |||||||||
Assessment of exposure | Representativeness of the exposed cohort | Selection of non-exposed cohort | Outcome of interest was not present at start | Comparability | Assessment of outcome | Enough follow-up | Adequacy of follow-up | Quality score | |
Guang et al. [12] | * | - | * | * | * | * | * | * | Good |
Hashem et al. [21] | * | - | * | * | * | * | * | * | Good |
Khodair et al. [18] | * | - | * | * | * | * | * | * | Good |
Publication bias
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1. What is the Doppler ultrasonography difference on the first postnatal day between neonates who developed NEC in comparison to those who did not?
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2. What is the Doppler ultrasonography difference at disease onset between neonates with and without NEC?