Hematocrit
Hematocrit is the share of blood volume made up of red cells. A US survey laboratory lists 38.7% to 51.4% for men and 32.0% to 45.9% for women aged 19 to 65. US recommendations define anemia as below 39.9% in men and 35.7% in women. Cohorts link both low and high values to more deaths. Standing raises a reading.
- Status
- Part of the complete blood count, ordered by a clinician and also sold direct to consumers by some US laboratories. FDA classifies automated hematocrit instruments as class II devices, and centrifuge-based hematocrit measuring devices as class II devices exempt from premarket notification [1][2].
- Measures
- The share of blood volume taken up by red blood cells, as a percentage. Automated analyzers calculate it from the red cell count and the mean cell volume, and older methods spin blood in a tube and read the packed cell layer [3][2].
- Also called
- Hct, HCT, hematocrit, haematocrit, packed cell volume, PCV, erythrocyte volume fraction, EVF, crit, CBC hematocrit
- Tested for
- anemia, blood loss, iron deficiency, polycythemia, erythrocytosis, monitoring testosterone therapy, blood donation eligibility, pregnancy check, living at altitude, general checkup
Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on
Linked in research4
- ModerateLinked to more deaths at both low and high hematocrit in an Iranian cohort of 49,983 adults and in the Framingham cohort.
- LimitedLimited evidence: one Norwegian cohort linked each 5-point rise in hematocrit to 25% more venous clots over 12.5 years.
- LimitedOne trial found a hematocrit target below 45% in polycythemia vera went with fewer cardiovascular deaths and major clots, 2.7% against 9.8% at a 45% to 50% target.
- LimitedLimited evidence: one database study linked a hematocrit of 52% or above on testosterone therapy to more heart events and clots in the first year, 5.15% against 3.87%.
Reported risks0
No risks sourced yet.
Reference ranges
Each range is the one its source published, in %. Also reported in L/L. Where sources differ, each is shown.
US national survey laboratory procedure manual, 2017 to 2018, men aged 19 to 65
Men aged 19 to 65, as the reference range used by the survey laboratory · [3]
| Range | What the source calls it |
|---|---|
| below 38.7 % | No name given |
| 38.7 to 51.4 % | "reference range" |
| above 51.4 % | No name given |
The 2.5th to 97.5th percentiles of everyone measured in the US National Health and Nutrition Examination Survey from 1999 to 2004, calculated by ranking, without screening out people with iron deficiency or illness. The analyzer calculates hematocrit as the red cell count times the mean cell volume, divided by 10. The manual lists dehydration, polycythemia, shock and chronic hypoxia among causes of a high result, and anemia, thalassemia and other hemoglobin disorders among causes of a low one [3].
US national survey laboratory procedure manual, 2017 to 2018, men aged 66 and older
Men aged 66 and older, as the reference range used by the survey laboratory · [3]
| Range | What the source calls it |
|---|---|
| below 33.9 % | No name given |
| 33.9 to 50.9 % | "reference range" |
| above 50.9 % | No name given |
Derived the same way from the 1999 to 2004 survey sample. The lower limit is 4.8 points under the limit for men aged 19 to 65 in the same table [3].
US national survey laboratory procedure manual, 2017 to 2018, women aged 19 to 65
Women aged 19 to 65, as the reference range used by the survey laboratory · [3]
| Range | What the source calls it |
|---|---|
| below 32 % | No name given |
| 32 to 45.9 % | "reference range" |
| above 45.9 % | No name given |
Derived the same way from the 1999 to 2004 survey sample, which was not screened for iron deficiency. The lower limit sits 3.7 points under the 1998 US anemia cutoff for women [3][4].
US national survey laboratory procedure manual, 2017 to 2018, women aged 66 and older
Women aged 66 and older, as the reference range used by the survey laboratory · [3]
| Range | What the source calls it |
|---|---|
| below 32.8 % | No name given |
| 32.8 to 47 % | "reference range" |
| above 47 % | No name given |
Derived the same way from the 1999 to 2004 survey sample [3].
US national survey laboratory procedure manual, 2017 to 2018, boys aged 1 to 5
Boys aged 1 to 5, as the reference range used by the survey laboratory · [3]
| Range | What the source calls it |
|---|---|
| below 32.1 % | No name given |
| 32.1 to 41.7 % | "reference range" |
| above 41.7 % | No name given |
Derived the same way from the 1999 to 2004 survey sample [3].
US national survey laboratory procedure manual, 2017 to 2018, boys aged 6 to 18
Boys aged 6 to 18, as the reference range used by the survey laboratory · [3]
| Range | What the source calls it |
|---|---|
| below 35.3 % | No name given |
| 35.3 to 49.9 % | "reference range" |
| above 49.9 % | No name given |
Derived the same way from the 1999 to 2004 survey sample [3].
US national survey laboratory procedure manual, 2017 to 2018, girls aged 1 to 5
Girls aged 1 to 5, as the reference range used by the survey laboratory · [3]
| Range | What the source calls it |
|---|---|
| below 32.5 % | No name given |
| 32.5 to 41.9 % | "reference range" |
| above 41.9 % | No name given |
Derived the same way from the 1999 to 2004 survey sample [3].
US national survey laboratory procedure manual, 2017 to 2018, girls aged 6 to 18
Girls aged 6 to 18, as the reference range used by the survey laboratory · [3]
| Range | What the source calls it |
|---|---|
| below 33.5 % | No name given |
| 33.5 to 44.6 % | "reference range" |
| above 44.6 % | No name given |
Derived the same way from the 1999 to 2004 survey sample [3].
US Centers for Disease Control and Prevention recommendations, 1998, men
Men aged 18 and older · [4]
| Range | What the source calls it |
|---|---|
| below 39.9 % | "anemia" |
| 39.9 or above % | No name given |
Based on the 5th percentile in the third US National Health and Nutrition Examination Survey, after excluding people with a high likelihood of iron deficiency. The matching hemoglobin cutoff is below 13.5 g/dL. The source reports that an Institute of Medicine panel advised lowering the hematocrit cutoff for Black adults by 2 points, and states that its own recommendations give no race-specific cutoffs because the reason for the difference has not been determined. No upper cutoff is given, so this block does not classify high results [4].
US Centers for Disease Control and Prevention recommendations, 1998, women
Nonpregnant and lactating women aged 18 and older · [4]
| Range | What the source calls it |
|---|---|
| below 35.7 % | "anemia" |
| 35.7 or above % | No name given |
Derived the same way as the cutoff for men. The matching hemoglobin cutoff is below 12.0 g/dL. The source describes hematocrit as a late indicator of iron deficiency that falls only after hemoglobin falls. No upper cutoff is given [4].
US Centers for Disease Control and Prevention recommendations, 1998, pregnancy, first trimester
Pregnant women in the first trimester · [4]
| Range | What the source calls it |
|---|---|
| below 33 % | "anemia" |
| 33 or above % | No name given |
The pregnancy cutoffs are based on clinical studies of European women who took iron supplements during pregnancy, because US data were lacking. The source also gives cutoffs by week of gestation, from 33.0% at 12 weeks to 32.0% at 16 to 28 weeks and 36.0% at 40 weeks. It advises referral to a physician familiar with anemia in pregnancy when hematocrit is below 27.0% [4].
US Centers for Disease Control and Prevention recommendations, 1998, pregnancy, second trimester
Pregnant women in the second trimester · [4]
| Range | What the source calls it |
|---|---|
| below 32 % | "anemia" |
| 32 to 45 % | No name given |
| above 45 % | No name given |
The source states that a hematocrit above 45.0% in pregnancy, more than 3 standard deviations over the reference mean, likely indicates poor expansion of blood volume, particularly in the second trimester, and calls for evaluation in the second or third trimester. It cites one study in which women with a hematocrit of 43% or above at 26 to 30 weeks had more than twice the risk of preterm delivery of women at 33% to 36%. It advises referral when hematocrit is below 27.0% [4].
US Centers for Disease Control and Prevention recommendations, 1998, pregnancy, third trimester
Pregnant women in the third trimester · [4]
| Range | What the source calls it |
|---|---|
| below 33 % | "anemia" |
| 33 to 45 % | No name given |
| above 45 % | No name given |
The upper line is the same 45.0% the source uses for the second trimester. It advises referral when hematocrit is below 27.0% [4].
US Centers for Disease Control and Prevention recommendations, 1998, children aged 1 to under 2
Children aged 1 to under 2 years · [4]
| Range | What the source calls it |
|---|---|
| below 32.9 % | "anemia" |
| 32.9 or above % | No name given |
Based on the 5th percentile in the third national survey after excluding children with a high likelihood of iron deficiency. The source states that this cutoff can also be used for infants aged 6 to 12 months, for whom the survey had no data. It reports an Institute of Medicine panel's advice to lower the cutoff by 1 point for Black children under 5. No upper cutoff is given [4].
US Centers for Disease Control and Prevention recommendations, 1998, children aged 2 to under 5
Children aged 2 to under 5 years · [4]
| Range | What the source calls it |
|---|---|
| below 33 % | "anemia" |
| 33 or above % | No name given |
Derived the same way. No upper cutoff is given [4].
US Centers for Disease Control and Prevention recommendations, 1998, children aged 5 to under 8
Children aged 5 to under 8 years · [4]
| Range | What the source calls it |
|---|---|
| below 34.5 % | "anemia" |
| 34.5 or above % | No name given |
Derived the same way. No upper cutoff is given [4].
US Centers for Disease Control and Prevention recommendations, 1998, children aged 8 to under 12
Children aged 8 to under 12 years · [4]
| Range | What the source calls it |
|---|---|
| below 35.4 % | "anemia" |
| 35.4 or above % | No name given |
Derived the same way. No upper cutoff is given [4].
US Centers for Disease Control and Prevention recommendations, 1998, boys aged 12 to under 15
Boys aged 12 to under 15 years · [4]
| Range | What the source calls it |
|---|---|
| below 37.3 % | "anemia" |
| 37.3 or above % | No name given |
Derived the same way. No upper cutoff is given [4].
US Centers for Disease Control and Prevention recommendations, 1998, boys aged 15 to under 18
Boys aged 15 to under 18 years · [4]
| Range | What the source calls it |
|---|---|
| below 39.7 % | "anemia" |
| 39.7 or above % | No name given |
Derived the same way. No upper cutoff is given [4].
US Centers for Disease Control and Prevention recommendations, 1998, girls aged 12 to under 15
Nonpregnant girls aged 12 to under 15 years · [4]
| Range | What the source calls it |
|---|---|
| below 35.7 % | "anemia" |
| 35.7 or above % | No name given |
Derived the same way. No upper cutoff is given [4].
US Centers for Disease Control and Prevention recommendations, 1998, girls aged 15 to under 18
Nonpregnant girls aged 15 to under 18 years · [4]
| Range | What the source calls it |
|---|---|
| below 35.9 % | "anemia" |
| 35.9 or above % | No name given |
Derived the same way. No upper cutoff is given [4].
Nordic Reference Interval Project, 2004, women
Women aged 18 to 90 in Denmark, Finland, Iceland, Norway and Sweden · [5]
| Range | What the source calls it |
|---|---|
| below 34.8 % | No name given |
| 34.8 to 45.9 % | "reference interval" |
| above 45.9 % | No name given |
The 2.5th to 97.5th percentiles in 1,826 healthy men and women, measured on 12 types of analyzer in 60 laboratories. Printed as a fraction, 0.348 to 0.459, under the name erythrocyte volume fraction. The lower limit is 2.8 points above the US survey manual's limit for women aged 19 to 65, which comes from a sample not screened for health [5][3].
Nordic Reference Interval Project, 2004, men
Men aged 18 to 90 in Denmark, Finland, Iceland, Norway and Sweden · [5]
| Range | What the source calls it |
|---|---|
| below 39.5 % | No name given |
| 39.5 to 50 % | "reference interval" |
| above 50 % | No name given |
Printed as 0.395 to 0.500, from the same healthy sample [5].
World Health Organization classification of blood cancers, 2016, polycythemia vera criterion, men
Men being assessed for polycythemia vera · [6]
| Range | What the source calls it |
|---|---|
| 49 or below % | No name given |
| above 49 % | "major criterion" |
One of three major criteria for diagnosing polycythemia vera, a bone marrow disorder. The others are a bone marrow biopsy finding and a JAK2 gene mutation, so a result above the threshold is not a diagnosis. The same criterion can be met by a hemoglobin above 16.5 g/dL or a raised red cell mass. For men the threshold sits inside the reference range of both the US survey manual and the Nordic project, and the authors report criticism that the matching hemoglobin threshold will send many people without the disorder for testing [6][3][5].
World Health Organization classification of blood cancers, 2016, polycythemia vera criterion, women
Women being assessed for polycythemia vera · [6]
| Range | What the source calls it |
|---|---|
| 48 or below % | No name given |
| above 48 % | "major criterion" |
One of three major criteria, as for men. The same criterion can be met by a hemoglobin above 16.0 g/dL [6].
What has been shown to move it
Shown to lower it3
Small drops in blood counts and albumin
Small drops in hematocrit, hemoglobin, white cells and albumin were seen on terazosin in trials, which the label attributes to blood dilution. PSA did not change.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- Small but statistically significant decreases in hematocrit, hemoglobin, white blood cells, total protein and albumin were seen in controlled trials. Treatment for up to 24 months had no significant effect on PSA [19].
- Population
- People in terazosin controlled trials [19].
- Sources
- [19]
- Caveats
- The label gives no size for the drops.
Fenofibrate: blood counts
The label reports mild to moderate drops in hemoglobin, hematocrit and white cells after starting fenofibrate that then stabilized, with rare low platelets or white cells.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- Mild to moderate decreases in hemoglobin, hematocrit and white blood cells were observed after starting fenofibrate and stabilized with long-term use. Thrombocytopenia and agranulocytosis have been reported [7].
- Population
- People starting fenofibrate [7].
- Sources
- [7]
- Caveats
- The label gives no sizes or rates.
Mouth sores, gut effects and blood count changes
Small trials found mouth sores, rash and gut problems in a few older adults, and falls in red cell counts without clinical effects.
Hemoglobin, hematocrit and red cell count fell on rapamycin, without clinical effects over the study.
The numbers and sources
- How common
- Very common: more than 1 in 10 people.
- Effect
- In the pilot, adverse effects on rapamycin were a facial rash (1), mouth sores (1) and gastrointestinal problems (2), against mouth sores (1) on placebo. Hemoglobin, hematocrit and red cell count fell on rapamycin, without clinical effects over the study [2]. In LAM, the label lists mouth sores, diarrhea, abdominal pain, nausea, acne and swelling among reactions in 20% or more [8].
- Population
- 25 older adults [2]; LAM patients in the label [8].
- Sources
- [2], [8]
- Caveats
- Small numbers. In PEARL, adverse events did not differ across groups [1].
Shown to raise it2
Anemia before fibroid surgery: leuprolide and other GnRH agonists
Shown to raise hemoglobin before fibroid surgery, by about 0.9 g/dL against placebo or no treatment, and with iron 75% reached target levels against 49% on iron alone.
Compared with iron alone [10]; placebo or no pretreatment [11]
The numbers and sources
- How common
- Very common: more than 1 in 10 people.
- Effect
- In women with hematocrit of 30% or less or hemoglobin of 10.2 g/dL or less, Lupron Depot 3.75 mg monthly with iron raised hemoglobin by a mean 4.2 g/dL and hematocrit by 10.1% at 3 months. At week 12, 75% on leuprolide with iron reached hematocrit of 36% and hemoglobin of 12 g/dL, against 49% on iron alone [10]. Across 10 trials of GnRH agonists before surgery, preoperative hemoglobin rose 0.88 g/dL more than with placebo or no pretreatment (95% CI 0.68 to 1.08, I² 0%, moderate certainty) [11].
- Population
- 104 women on leuprolide with iron and 98 on iron alone [10]; 834 premenopausal women in 10 trials [11].
- Sources
- [10], [11]
- Caveats
- The Cochrane review pools GnRH agonists as a class, not leuprolide alone [11]. The label notes some women may benefit from iron alone or from 1 to 2 months of treatment [10].
Higher red blood cell concentration
Shown to raise hematocrit, with 2.7% to 3.5% of people moving above the reference range on empagliflozin against 0.6% on placebo.
The numbers and sources
- How common
- Common: between 1 in 100 and 1 in 10 people.
- Effect
- In pooled empagliflozin trials, median hematocrit rose by 2.8% on either dose and fell by 1.3% on placebo. Among people who started in the reference range, 2.7% on 10 mg and 3.5% on 25 mg ended above it against 0.6% on placebo [20]. In pooled dapagliflozin trials, a hematocrit above 55% was recorded in 1.3% on 10 mg against 0.4% on placebo by week 24 [23].
- Population
- Adults with type 2 diabetes in pooled placebo-controlled trials [20][23].
- Sources
- [20], [23]
- Caveats
- A laboratory change. The labels do not report clinical events tied to it.
How it compares with the reference method
Mixed results1
Variation from one draw to the next in one person
Shown to vary about 2.8% from one draw to the next within the same person, in a pooled estimate from a European laboratory federation.
The numbers and sources
- Compared with
- The same person's results on repeated venous draws
- Effect
- The European Federation of Clinical Chemistry and Laboratory Medicine database gives a pooled within-person variation of 2.8% for hematocrit, with lower and upper limits of 2.2% and 3.1%, from 7 included estimates. Variation between people is 5.6% [14]. At a hematocrit of 45%, 2.8% is about 1.3 points.
- Population
- Healthy adults in the studies the database pools [14].
- Sources
- [14]
- Caveats
- A summary across studies in healthy volunteers. The database states no threshold for agreement, so the result is given as numbers only [14].
Did not match the reference method2
Posture at the blood draw
One study of 19 volunteers found hematocrit read about 1.7% higher sitting and 6.9% higher standing than lying down.
The numbers and sources
- Compared with
- The same people's blood drawn after 25 minutes lying down
- Effect
- Median hematocrit was 41% after 25 minutes lying down, 42% after 20 minutes sitting and 44% after 20 minutes standing. The relative change was 1.7% from lying to sitting, 6.9% from lying to standing and 5.3% from sitting to standing, each at or above the 1.7% limit for bias the authors took from biological variation. Plasma volume fell 14.1% from lying to standing [13]. The 1998 US recommendations add that squeezing the finger during a capillary sample mixes tissue fluid into the blood and gives falsely low readings, and that variation across the day is small [4].
- Population
- 19 healthy laboratory staff in Italy, 7 men and 12 women, mean age 44 [13].
- Sources
- [13], [4]
- Caveats
- One small study on one analyzer. The changes are percentages of the reading, so 6.9% of a hematocrit of 41 is about 3 points [13].
Altitude and smoking
Limited evidence: US recommendations raise the anemia cutoff by 0.5 points at 3,000 feet, 6.0 points at 10,000 feet and 1.0 to 2.0 points in smokers.
The numbers and sources
- Compared with
- Hematocrit in nonsmokers living below 3,000 feet
- Effect
- The 1998 US recommendations state that long-term residence at 3,000 feet or higher and cigarette smoking shift hematocrit upward, and adjust the anemia cutoff to match. The adjustments in hematocrit points are 0.5 at 3,000 to 3,999 feet, 1.0 at 4,000 to 4,999, 1.5 at 5,000 to 5,999, 2.0 at 6,000 to 6,999, 3.0 at 7,000 to 7,999, 4.0 at 8,000 to 8,999, 5.0 at 9,000 to 9,999 and 6.0 at 10,000 to 11,000 feet. For smoking they are 1.0 at half a pack to under 1 pack a day, 1.5 at 1 to under 2 packs, 2.0 at 2 packs or more, and 1.0 for smokers as a whole [4].
- Population
- US survey and surveillance data cited by the recommendations [4].
- Sources
- [4]
- Caveats
- The figures are taken from the recommendations, not from the studies behind them, and date from 1998. The source states that screening is less accurate when cutoffs are not adjusted for these two factors [4].
What studies tie it to
Linked in research4
Death from any cause
Linked to more deaths at both low and high hematocrit in an Iranian cohort of 49,983 adults and in the Framingham cohort.
The numbers and sources
- Effect
- In 49,983 Iranian adults followed for a mean of 5 years, the relation between hematocrit and death was U-shaped in both sexes. In women, against 35% to 39%, adjusted hazard ratios for death were 2.12 (95% CI 1.26 to 3.58) at 15% to 29%, 1.58 (1.29 to 1.93) at 45% to 49% and 2.05 (1.17 to 3.60) at 50% to 54%. In men, against 40% to 44%, they were 2.12 (1.30 to 3.45) at 15% to 29%, 1.64 (1.22 to 2.21) at 30% to 34% and 1.29 (1.04 to 1.61) at 50% to 54%. Deaths from cardiovascular disease followed the same pattern [7]. In the Framingham cohort over 34 years, people in the highest fifth of hematocrit had more deaths from any cause and more cardiovascular disease, and women with lower values also had more cardiovascular events, which the authors describe as a J-shaped or U-shaped relation [8].
- Population
- 49,983 adults aged 40 to 75 in the Golestan Cohort Study in northeast Iran, 2,262 deaths [7]. 5,209 men and women in the Framingham cohort [8].
- Sources
- [7], [8]
- Caveats
- Observational. In the Iranian cohort, leaving out the first 2 years of follow-up weakened the association at low hematocrit in both sexes and removed the association at high hematocrit in men, which points to illness before death as part of the explanation. That cohort measured hematocrit by spinning blood in a tube, not by analyzer [7]. The Framingham abstract gives no hazard ratios [8].
Blood clots in the veins
Limited evidence: one Norwegian cohort linked each 5-point rise in hematocrit to 25% more venous clots over 12.5 years.
The numbers and sources
- Effect
- The hazard ratio for venous thromboembolism per 5-point increase in hematocrit was 1.25 (95% CI 1.08 to 1.44), and 1.37 (1.10 to 1.71) for clots with no provoking cause, after adjustment for age, body mass index and smoking. Men in the top fifth of hematocrit, 46% or above, had 1.5 times the risk of any venous clot (95% CI 1.08 to 2.21) and 2.4 times the risk of an unprovoked clot (1.36 to 4.15) of men in the lowest two fifths. Estimates were higher for men than for women [9].
- Population
- 26,108 adults in the Tromsø Study in Norway, 447 venous clots over a median of 12.5 years [9].
- Sources
- [9]
- Caveats
- One observational cohort. Findings for hemoglobin and red cell count were similar, so the study cannot separate hematocrit from them [9].
Cardiovascular death and clots in a trial that held hematocrit below 45% in polycythemia vera
One trial found a hematocrit target below 45% in polycythemia vera went with fewer cardiovascular deaths and major clots, 2.7% against 9.8% at a 45% to 50% target.
The numbers and sources
- Effect
- Adults with JAK2-positive polycythemia vera were assigned to treatment aimed at a hematocrit below 45% or at 45% to 50%. After a median of 31 months, death from cardiovascular causes or a major clot had occurred in 5 of 182 patients in the lower target group (2.7%) and 18 of 183 in the higher target group (9.8%), a hazard ratio in the higher target group of 3.91 (95% CI 1.45 to 10.53). The rate of adverse events did not differ significantly between groups [10].
- Population
- 365 adults with polycythemia vera in Italy, treated with phlebotomy, hydroxyurea or both [10].
- Sources
- [10]
- Caveats
- One trial of 365 people with a bone marrow disorder that raises red cell production, so it does not show what a hematocrit of 45% to 50% means in people without that disorder [10].
Heart events and clots at a hematocrit of 52% or above in men on testosterone therapy
Limited evidence: one database study linked a hematocrit of 52% or above on testosterone therapy to more heart events and clots in the first year, 5.15% against 3.87%.
The numbers and sources
- Effect
- Among men with low testosterone who received testosterone therapy, 5,842 who reached a hematocrit of 52% or above were matched to 5,842 who did not. A major cardiovascular event or venous clot in the first year occurred in 301 (5.15%) against 226 (3.87%), an odds ratio of 1.35 (95% CI 1.13 to 1.61). Among men whose hematocrit stayed under 52%, the odds were similar with and without testosterone therapy (odds ratio 1.07, 0.98 to 1.18). The authors report that national guidelines stop or change therapy at thresholds between 50% and 55%, and that the basis for those thresholds is not cited in the guidelines [12].
- Population
- Men over 18 with total testosterone below 350 ng/dL in a US multi-institution records database, 86% white [12].
- Sources
- [12]
- Caveats
- Retrospective, from medical records. Men who reached 52% started with a higher hematocrit, a mean of 47.4%, and the groups could not be matched on it, so the authors cannot say whether the risk comes from reaching 52% or from the higher starting value. The guideline thresholds are quoted from this study, not from the guidelines themselves [12].
Checked, no link found1
Death and heart attack in a dialysis trial that raised hematocrit to 42%
One trial found raising hematocrit to 42% with epoetin did not cut deaths or heart attacks in hemodialysis patients with heart disease, and the trial was halted.
The numbers and sources
- Effect
- Patients were assigned to epoetin doses aimed at a hematocrit of 42% or of 30%. After 29 months there were 183 deaths and 19 first nonfatal heart attacks in the 42% group and 150 deaths and 14 nonfatal heart attacks in the 30% group, a risk ratio of 1.3 (95% CI 0.9 to 1.9). The difference did not reach the preset stopping boundary, and the study was halted. Within each group, death rates fell as the hematocrit reached rose [11].
- Population
- 1,233 people on hemodialysis with heart failure or ischemic heart disease, treated for a median of 14 months [11].
- Sources
- [11]
- Caveats
- One trial in people on dialysis with heart disease, in whom hematocrit was raised with a drug. The higher target group also had a decline in the adequacy of dialysis and more intravenous iron, so the trial cannot separate hematocrit from the treatment used to raise it [11].
- Why limited
- This rests on one trial, of 1,233 people. Strength counts independent studies that agree, so one trial is limited at any size.
Related
Sources
- US Food and Drug Administration. 21 CFR 864.5600, Automated hematocrit instrument. Electronic Code of Federal Regulations. https://www.ecfr.gov/current/title-21/section-864.5600
- US Food and Drug Administration. 21 CFR 864.6400, Hematocrit measuring device. Electronic Code of Federal Regulations. https://www.ecfr.gov/current/title-21/section-864.6400
- Centers for Disease Control and Prevention, National Center for Health Statistics. National Health and Nutrition Examination Survey 2017-2018 Laboratory Procedure Manual: Complete Blood Count, whole blood, Beckman Coulter DxH 800 analyzer. Performed by the NHANES Mobile Examination Center. https://wwwn.cdc.gov/nchs/data/nhanes/public/2017/labmethods/CBC-J-MET-508.pdf
- Centers for Disease Control and Prevention. Recommendations to Prevent and Control Iron Deficiency in the United States. MMWR Recommendations and Reports. 1998;47(RR-3). https://www.cdc.gov/mmwr/preview/mmwrhtml/00051880.htm
- Nordin G, Mårtensson A, Swolin B, et al. A multicentre study of reference intervals for haemoglobin, basic blood cell counts and erythrocyte indices in the adult population of the Nordic countries. Scandinavian Journal of Clinical and Laboratory Investigation. 2004. https://doi.org/10.1080/00365510410002797
- Barbui T, Thiele J, Gisslinger H, et al. The 2016 WHO classification and diagnostic criteria for myeloproliferative neoplasms: document summary and in-depth discussion. Blood Cancer Journal. 2018. https://doi.org/10.1038/s41408-018-0054-y
- Boffetta P, Islami F, Vedanthan R, et al. A U-shaped relationship between haematocrit and mortality in a large prospective cohort study. International Journal of Epidemiology. 2013. https://doi.org/10.1093/ije/dyt013
- Gagnon DR, Zhang TJ, Brand FN, Kannel WB. Hematocrit and the risk of cardiovascular disease, the Framingham Study: a 34-year follow-up. American Heart Journal. 1994. https://doi.org/10.1016/0002-8703(94)90679-3
- Braekkan SK, Mathiesen EB, Njølstad I, Wilsgaard T, Hansen JB. Hematocrit and risk of venous thromboembolism in a general population. The Tromsø study. Haematologica. 2010. https://doi.org/10.3324/haematol.2009.008417
- Marchioli R, Finazzi G, Specchia G, et al. Cardiovascular Events and Intensity of Treatment in Polycythemia Vera. New England Journal of Medicine. 2013. https://doi.org/10.1056/NEJMoa1208500
- Besarab A, Bolton WK, Browne JK, et al. The Effects of Normal as Compared with Low Hematocrit Values in Patients with Cardiac Disease Who Are Receiving Hemodialysis and Epoetin. New England Journal of Medicine. 1998. https://doi.org/10.1056/NEJM199808273390903
- Ory J, Nackeeran S, Balaji NC, Hare JM, Ramasamy R. Secondary Polycythemia in Men Receiving Testosterone Therapy Increases Risk of Major Adverse Cardiovascular Events and Venous Thromboembolism in the First Year of Therapy. Journal of Urology. 2022. https://doi.org/10.1097/JU.0000000000002437
- Lima-Oliveira G, Guidi GC, Salvagno GL, et al. Patient posture for blood collection by venipuncture: recall for standardization after 28 years. Revista Brasileira de Hematologia e Hemoterapia. 2017. https://doi.org/10.1016/j.bjhh.2017.01.004
- European Federation of Clinical Chemistry and Laboratory Medicine. EFLM Biological Variation Database, meta-analysis estimates, read 2026-11-13. https://biologicalvariation.eu/