Stovell MG, Mada MO, Carpenter TA, et al. Phosphorus spectroscopy in acute TBI demonstrates metabolic changes that relate to outcome in the presence of normal structural MRI. J Cereb Bld Flow. Epub ahead of print 18 September 2018. DOI: 10.1177/0271678X18799176.
The authors wish to make the following corrections.
In the Results section of this article, in the section titled 31P MRS: metabolic changes in acute TBI, the sentence that reads
PCr/γATP was higher in TBI patients (Figure 2(a)): median (and interquartile range, IQR) PCr/γATP was 1.09 (1.00–1.22) in TBI patients and 0.91 (0.84–0.97) in healthy controls (p<0.0001).
has been corrected:
PCr/γATP was higher in TBI patients (Figure 2(a)): median (and interquartile range, IQR) PCr/γATP was 1.09 (1.04–1.20) in TBI patients and 0.93 (0.86–0.96) in healthy controls (p<0.0001).
The sentence that reads
TBI patients' brain pH was more alkaline than that of healthy controls (Figure 2(b)): median 7.03 (7.00–7.08) in TBI patients; and 7.00 (6.98–7.01) in healthy controls (p = 0.006).
has been corrected:
TBI patients' brain pH was more alkaline than that of healthy controls (Figure 2(b)): median 7.04 (7.02–7.05) in TBI patients; and 7.00 (6.99–7.00) in healthy controls (p<0.006).
The sentence that reads
This association was not strong (Spearman's correlation coefficient rho = 0.27), although highly statistically significant (p<0.0005).
has been corrected:
This association was not strong (Spearman's correlation coefficient rho = 0.27), although highly statistically significant (p<0.0001).
The sentence that reads
Grey matter/white matter ratio was not significantly different between TBI patients and healthy controls (p = 0.19, Mann-Whitney), nor did it reach significance as a covariate in linear mixed model analysis of PCr/γATP, PCr/total-mobilephosphate or pH.
has been corrected:
Grey matter/white matter ratio was not significantly different between TBI patients and healthy controls (p = 0.26, Mann-Whitney), nor did it reach significance as a covariate in linear mixed model analysis of PCr/γATP, PCr/total-mobilephosphate or pH.
The sentence that reads
However, it was a statistically significant covariate in linear mixed model analysis of γATP/total-mobile-phosphate (p = 0.0014), and as it can affect ratios of high-energy phosphates in the healthy brain,14,22 it was included in all mixed effects model analysis.
has been corrected:
However, it was a statistically significant covariate in linear mixed model analysis of γATP/total-mobile-phosphate (p = 0.03), and as it can affect ratios of high-energy phosphates in the healthy brain,14,22 it was included in all mixed effects model analysis.
In the Results section of this article, in the section titled 31P MRS: metabolic changes by outcome, the sentence that reads
Brain alkalosis (pH) was higher in patients with unfavourable outcome than patients with favourable outcome using both analytical methods (p<0.02) (Table 2).
Table 2.
Summary of 31P MRS results: group medians and interquartile ranges of within-subject means.
| Number subjects | Injured voxels | PCr/γATP Median (IQR) | PCr/total Median (IQR) | γATP/total Median (IQR) | pH Median (IQR) | |
|---|---|---|---|---|---|---|
| TBI: all patients | 13 | Including | 1.09 (1.04–1.20) | 0.47 (0.46–0.48) | 0.44 (0.40–0.45) | 7.04 (7.02–7.05) |
| Excluding | 1.07 (1.06–1.21) | 0.47 (0.46–0.49) | 0.44 (0.40–0.45) | 7.03 (7.01–7.05) | ||
| Healthy controls | 10 | NA | 0.93 (0.86–0.96) | 0.42 (0.41–0.43) | 0.46 (0.45–0.48) | 7.00 (6.99–7.00) |
| p (TBI vs. HC) | Including | <0.0001 | <0.0001 | 0.0009 | 0.042 | |
| Excluding | <0.0001 | <0.0001 | 0.001 | 0.055 | ||
| TBI: favourable outcome | 7 | Including | 1.07 (1.04–1.10) | 0.48 (0.46–0.48) | 0.44 (0.44–0.45) | 7.02 (7.00–7.03) |
| Excluding | 1.07 (1.06–1.09) | 0.47 (0.46–0.48) | 0.44 (0.44–0.45) | 7.02 (7.00–7.03) | ||
| TBI: unfavourable outcome | 6 | Including | 1.14 (1.07–1.22) | 0.47 (0.46–0.49) | 0.41 (0.39–0.42) | 7.07 (7.04–7.14) |
| Excluding | 1.14 (1.06–1.24) | 0.48 (0.47–0.49) | 0.41 (0.40–0.44) | 7.07 (7.03–7.16) | ||
| p (Fav vs. Unfav.) | Including | 0.3 | 0.9 | 0.04 | 0.03 | |
| Excluding | 0.3 | 0.9 | 0.06 [0.04] | 0.057 [0.008] |
Note: 31P magnetic resonance spectroscopy (MRS) measurements of pH, phosphocreatine (PCr), adenosine triphosphate (γATP) and ‘total' mobile phosphate (PCr + γATP + inorganic phosphorus) ratios in 13 patients suffering from acute major traumatic brain injury (TBI) and 10 age-group matched healthy controls (HC). Results represent group medians of within-subject means, with interquartile ranges (IQR) in parentheses (curved brackets); for each individual subject's mean values see Table 3. Voxels were considered injured if they contained ≥5% radiological injury on fluid-attenuated inversion recovery (FLAIR) or susceptibility weighted injury (SWI) MR sequences. Favourable outcome (Fav) defined as six-month Glasgow outcome score (extended) (GOS-E) ≥4, and unfavourable outcome (Unfav.) GOS-E ≤ 3. Statistical analysis performed using a linear mixed model in R (lme in package nlme), adjusting for voxel grey matter/white ratio. Inclusion of healthy controls and analysis of the linear model using glht (results in Figure 4) found the difference in γATP/total-mobile-phosphate to be statistically significant (results in square [ ] brackets), but did not affect the significance of other measurements.
has been corrected:
Brain alkalosis (pH) was higher in patients with unfavourable outcome than patients with favourable outcome using both analytical methods (p<0.03) (Table 2).
In the Results section of this article, in the section titled 31P MRS: metabolic changes in the absence of visible tissue injury, the sentence that reads
The difference in γATP/total-mobile-phosphate narrowly lost significance, both by lme (p = 0.076) and by Mann-Whitney (p = 0.18).
has been corrected:
The difference in γATP/total-mobile-phosphate narrowly lost significance, both by lme (p = 0.06) and by Mann-Whitney (p = 0.18).
In Figure 4, there is a change to the second p value in part (a). It previously read p = 0.37 and has been corrected as below, p = 0.28.
Figure 4.
In Table 2, the value of p (Fav vs Unfav.) in the column PCr/total Median (IQR) and the value of p (TBI vs. HC) in the column pH Median (IQR) have been corrected as below.
In Table 3, the values of H01-H10 in column PCr/γATP should have appeared as below.
Table 3.
31P MRS data acquired from TBI patients and healthy controls.
| Subject ID | PCr/γATP mean | PCr/γATP S.D. | PCr/total mean | PCr/total S.D. | γATP/total mean | γATP/total S.D. | pH mean | pH S.D. | No. of voxels |
|---|---|---|---|---|---|---|---|---|---|
| P01 | 1.06 | 0.11 | 0.47 | 0.03 | 0.45 | 0.02 | 7.03 | 0.09 | 7 |
| P02 | 1.10 | 0.17 | 0.48 | 0.04 | 0.44 | 0.03 | 7.02 | 0.03 | 7 |
| P03 | 1.41 | 0.13 | 0.52 | 0.04 | 0.37 | 0.03 | 7.29 | 0.07 | 7 |
| P04 | 1.00 | 0.12 | 0.42 | 0.06 | 0.42 | 0.04 | 7.15 | 0.09 | 7 |
| P05 | 1.09 | 0.23 | 0.46 | 0.06 | 0.42 | 0.04 | 7.10 | 0.07 | 4 |
| P06 | 1.07 | 0.14 | 0.48 | 0.04 | 0.45 | 0.02 | 7.01 | 0.07 | 6 |
| P07 | 1.03 | 0.13 | 0.45 | 0.03 | 0.45 | 0.02 | 6.98 | 0.02 | 8 |
| P08 | 1.21 | 0.13 | 0.48 | 0.04 | 0.40 | 0.04 | 7.02 | 0.06 | 8 |
| P09 | 1.20 | 0.04 | 0.47 | 0.02 | 0.39 | 0.02 | 7.05 | 0.05 | 6 |
| P10 | 1.23 | 0.09 | 0.49 | 0.03 | 0.40 | 0.03 | 7.04 | 0.02 | 7 |
| P11 | 1.04 | 0.05 | 0.46 | 0.01 | 0.44 | 0.02 | 7.04 | 0.02 | 7 |
| P12 | 1.04 | 0.08 | 0.46 | 0.03 | 0.44 | 0.01 | 7.04 | 0.07 | 8 |
| P13 | 1.10 | 0.28 | 0.50 | 0.06 | 0.46 | 0.05 | 6.96 | 0.06 | 8 |
| H01 | 0.95 | 0.07 | 0.42 | 0.02 | 0.45 | 0.01 | 6.99 | 0.02 | 8 |
| H02 | 0.74 | 0.07 | 0.37 | 0.02 | 0.50 | 0.02 | 7.00 | 0.02 | 8 |
| H03 | 0.92 | 0.04 | 0.42 | 0.03 | 0.46 | 0.03 | 7.00 | 0.04 | 8 |
| H04 | 0.98 | 0.05 | 0.44 | 0.02 | 0.45 | 0.01 | 7.00 | 0.01 | 8 |
| H05 | 0.82 | 0.05 | 0.40 | 0.02 | 0.49 | 0.03 | 6.99 | 0.02 | 8 |
| H06 | 0.99 | 0.04 | 0.45 | 0.01 | 0.45 | 0.01 | 6.97 | 0.03 | 8 |
| H07 | 0.95 | 0.06 | 0.43 | 0.02 | 0.45 | 0.01 | 7.00 | 0.01 | 8 |
| H08 | 0.88 | 0.04 | 0.42 | 0.02 | 0.48 | 0.01 | 6.99 | 0.04 | 8 |
| H09 | 0.86 | 0.04 | 0.41 | 0.01 | 0.48 | 0.01 | 7.00 | 0.03 | 8 |
| H10 | 0.97 | 0.04 | 0.43 | 0.03 | 0.45 | 0.03 | 7.03 | 0.03 | 8 |
Note: Individual subject 31P magnetic resonance spectroscopy (MRS) measurements of pH, phosphocreatine (PCr), adenosine triphosphate (γATP) and ‘total’ mobile phosphate (PCr + γATP + inorganic phosphorus (Pi)) ratios derived from the central eight voxels of 13 TBI patients (P1-P13) and 10 age-group-matched healthy controls (H1-H10). As part of a separate biochemical study, some patients had microdialysis catheters supplemented with either succinate or glucose so a voxel was excluded from analysis (P01, P02, P03, P04, P05, P06, P10, P11). Two subjects’ CSI grids were positioned to capture superficially placed microdialysis catheters, excluding a further one (P06 and P09) and three (P05) voxels that represented < 90% brain tissue.