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Risk of bias graph: review authors' judgements about each risk of bias item presented as percentages across all included studies.

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Figure 1

Risk of bias graph: review authors' judgements about each risk of bias item presented as percentages across all included studies.

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Risk of bias summary: review authors' judgements about each risk of bias item for each included study.

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Figure 2

Risk of bias summary: review authors' judgements about each risk of bias item for each included study.

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Comparison 1: 1 mg versus 5 mg oral vitamin k, Outcome 1: Serum % uncarboxylated osteocalcin

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Analysis 1.1

Comparison 1: 1 mg versus 5 mg oral vitamin k, Outcome 1: Serum % uncarboxylated osteocalcin

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Comparison 1: 1 mg versus 5 mg oral vitamin k, Outcome 2: Serum vitamin k levels

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Analysis 1.2

Comparison 1: 1 mg versus 5 mg oral vitamin k, Outcome 2: Serum vitamin k levels

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Summary of findings 1. Vitamin K compared to control for people with cystic fibrosis

Vitamin K compared to control for people with cystic fibrosis

Patient or population: people with cystic fibrosis
Setting: community or health care facilities
Intervention: vitamin K
Comparison: placebo or no intervention

Outcomes

Anticipated absolute effects* (95% CI)

Relative effect
(95% CI)

№ of participants
(studies)

Certainty of the evidence
(GRADE)

Comments

Risk with Placebo

Risk with Vitamin K

Time to cessation of bleeding

Follow‐up: 12 months

Outcome not reported.

Bone mineral density: lumbar spine z score

Follow‐up: 12 months

The mean (SD) change in the placebo group in z score at the lumbar spine was 0.041 (0.15) g/cm³ and in the treatment group it was ‐0.073 (0.30) g/cm³.

38 (1)

Very low

⊕⊝⊝⊝a,b

The trial authors also reported mean change in z score in those participants 25 or under and those that were over 25 years. They concluded that vitamin K had no significant effect except in participants that were over 25 years. where vitamin K may have a protective effect against decline in BMD (Kuitert 2010).

The mean (SD) change in the placebo group at the femoral hip z score was 0.053 (0.19) g/cm³ and in the treatment group was ‐0.20 (0.31) g/cm³. The mean change in femoral hip z score ≤ 25, but there is not enough information to comment on the statistical significance of this.

The authors report no significant effect of vitamin K on bone mineral density.

QoL: CFQ‐R

Follow‐up:12 months

Outcome not reported.

QoL: CFQoL

Follow‐up: 12 months

Outcome not reported.

Adverse events

Follow‐up: 12 months

Outcome not reported.

PIVKA II levels: change in PIVKA II (ng/mL)

Follow‐up: 12 months

Mean (SD) PIVKA‐II concentrations increased significantly when participants were not supplemented (5.1 (3.2) ng/mL in the supplemented group and 21.8 (3.2) ng/mL in the unsupplemented group) and almost one third (5 out of 18) of the participants had PIVKA‐II levels within the normal range (≤ 2 ng/mL) following supplementation.

18 (1 study)

Very low

⊕⊝⊝⊝b,c

Uncarboxylated osteocalcin:

change in carboxylation of osteocalcin (% Glu‐OC)

Follow‐up: 1 month

See comments.

Two studies (total n = 56) narratively reported that vitamin K improved carboxylation of osteocalcin (Beker 1997; Kuitert 2010).

*The risk in the intervention group (and its 95% CI) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).

CI: confidence interval; CFQoL: Cystic Fibrosis Quality of Life; CFQ‐R: Cystic Fibrosis Questionnaire ‐ Revised; PIVKA‐II: proteins induced by vitamin K absence; SD: standard deviation.

GRADE Working Group grades of evidence
High certainty: we are very confident that the true effect lies close to that of the estimate of the effect.
Moderate certainty: we are moderately confident in the effect estimate. The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different
Low certainty: our confidence in the effect estimate is limited. The true effect may be substantially different from the estimate of the effect
Very low certainty: we have very little confidence in the effect estimate.The true effect is likely to be substantially different from the estimate of effect

a Downgraded twice due to an unclear risk of bias in one RCT, particularly for the domains of randomisation, allocation concealment and blinding.

b Downgraded once due to imprecision as numbers were too low to meet the optimal information size.

c Downgraded twice due to risk of bias within one RCT. The randomisation and allocation concealment processes were unclear and it wasn't possible to blind either participants or healthcare providers. It was unclear whether the outcome assessors were blinded.

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Summary of findings 1. Vitamin K compared to control for people with cystic fibrosis
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Summary of findings 2. Comparison of different vitamin K doses for people with cystic fibrosis

High‐dose vitamin K compared to low‐dose vitamin K for people with cystic fibrosis

Patient or population: people with cystic fibrosis
Setting: community or health care facilities
Intervention: high‐dose vitamin K
Comparison: low‐dose vitamin K

Outcomes

Anticipated absolute effects* (95% CI)

Relative effect
(95% CI)

№ of participants
(studies)

Certainty of the evidence
(GRADE)

Comments

Risk with low‐dose vitamin K

Risk with high‐dose vitamin K

Time to cessation of bleeding

Follow‐up: 12 months

Outcome not reported.

Bone mineral density: lumbar spine z score

Follow‐up: 12 months

Outcome not reported.

QoL: CFQ‐R

Follow‐up:12 months

Outcome not reported.

QoL: CFQoL

Follow‐up: 12 months

Outcome not reported.

Adverse events

Follow‐up: 12 months

Outcome not reported.

PIVKA II levels: change in PIVKA II (ng/mL)

Follow‐up: 12 months

Outcome not reported.

Uncarboxylated osteocalcin:

change in carboxylation of osteocalcin level (% Glu‐OC)

Follow‐up: 1 month

Uncarboxylated osteocalcin was 2.20% lower in the 1 mg group than in the 5 mg group (14.33% lower to 9.93% higher).

13 (1 study)

Very low

⊕⊝⊝⊝a,b

*The risk in the intervention group (and its 95% CI) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).

CI: confidence interval; CFQoL: Cystic Fibrosis Quality of Life; CFQ‐R: Cystic Fibrosis Questionnaire ‐ Revised; PIVKA‐II: proteins induced by vitamin K absence; SD: standard deviation.

GRADE Working Group grades of evidence
High certainty: we are very confident that the true effect lies close to that of the estimate of the effect.
Moderate certainty: we are moderately confident in the effect estimate. The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different
Low certainty: our confidence in the effect estimate is limited. The true effect may be substantially different from the estimate of the effect
Very low certainty: we have very little confidence in the effect estimate.The true effect is likely to be substantially different from the estimate of effect

a Downgraded once due to imprecision as numbers were too low to meet the optimal information size.

b Downgraded twice due to risk of bias within the single RCT. There was an unclear risk of bias across four of the six domains, particularly around randomisation, allocation conclealment and blinding. This was a cross‐over trial with no wash‐out period and there was therefore a potential carry‐over of treatment effect. No first‐period data were available.

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Summary of findings 2. Comparison of different vitamin K doses for people with cystic fibrosis
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Table 1. Serum undercarboxylated osteocalcin (ucOC) percentage (Drury 2008)

Dose

n

UcOC %
Baseline mean (SD)

UcOC %
End of study mean (SD)

1 mg/day

7

46 (14.4)

28 (8.26)

5 mg/day

6

47.6 (9.45)

30.2 (13.09)

SD: standard deviation
ucOC: undercarboxylated osteocalcin

Figuras y tablas -
Table 1. Serum undercarboxylated osteocalcin (ucOC) percentage (Drury 2008)
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Table 2. Serum vitamin K levels (Drury 2008)

Dose

n

Serum vitamin K levels (nmol/L)
Baseline mean (SD)

Serum vitamin K levels (nmol/L)
End of study mean (SD)

1 mg/day

7

0.28 (0.25)

2.52 (2.61)

5 mg/day

6

0.15 (0.19)

6.98 (9.95)

SD: standard deviation
Figuras y tablas -
Table 2. Serum vitamin K levels (Drury 2008)
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Comparison 1. 1 mg versus 5 mg oral vitamin k

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1.1 Serum % uncarboxylated osteocalcin Show forest plot

1

Mean Difference (IV, Fixed, 95% CI)

Subtotals only

1.1.1 Short term (up to 12 months)

1

13

Mean Difference (IV, Fixed, 95% CI)

‐2.20 [‐14.33, 9.93]

1.2 Serum vitamin k levels Show forest plot

1

Mean Difference (IV, Fixed, 95% CI)

Subtotals only

1.2.1 Short term (up to 12 months)

1

13

Mean Difference (IV, Fixed, 95% CI)

‐4.46 [‐12.65, 3.73]
Figuras y tablas -
Comparison 1. 1 mg versus 5 mg oral vitamin k
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