J Clin Med Res

Journal of Clinical Medicine Research, ISSN 1918-3003 print, 1918-3011 online, Open Access

Article copyright, the authors; Journal compilation copyright, J Clin Med Res and Elmer Press Inc

Journal website http://www.jocmr.org

Letter to the Editor

Volume 6, Number 5, October 2014, pages 395-397

Secondary Polycythemia and the Risk of Venous Thromboembolism

**Table 1.** Secondary Polycythemia and the Risk of Venous Thromboembolism in Adults
Author, year	Study groups (N)	Age in years	Etiology of PCT	Definition of PCT	Average HCT	Outcomes	Strength	Limitation
CHD: congenital heart disease; Comp: compensated; COPD: chronic obstructive pulmonary disease; DVT: deep venous thrombosis; HCT: hematocrit; Hgb: hemoglobin; N: number of patients; NS: not significant; PCT: polycythemia; PE: pulmonary embolism; PV: polycythemia vera; RBC: red blood cell; SP: secondary polycythemia; Uncomp: uncompensated; VTE: venous thromboembolism. All studies, except by Ristic et al [4], were retrospective. *The study included patients who presented with respiratory distress, and were found to have elevated D-dimer. †Obesity was identified as a possible risk factor for venous thromboembolism in secondary polycythemia. ‡A 28-year-old female with iron-deficient polycythemia had four episodes of amaurosis fugax during few months when hematocrit level ranged between 63% and 73%. §In smoking-related secondary polycythemia, there was only one venous thromboembolism and 11 arterial events (myocardial infarction, stroke or transient ischemic attacks). Risk of venous thromboembolism was 4% vs. 21% in secondary polycythemia compared to polycythemia vera. The incidence of recurrent events was higher in polycythemia vera compared to secondary polycythemia (28% vs. 7%). Within secondary polycythemia, patients who had an event had lower hematocrit and platelet count than those who did not have an event.
Ristic et al, 2013 [4]	PCT (100) vs. non-PCT (262)	66 vs. 63	COPD/respiratory failure	HCT > 50%	58% vs. 40%	PE 39% vs. 11% (P < 0.001); DVT 5% vs. 4% (P = 0.87)	Only prospective study	Inclusion criteria,* unmatched groups, smoking habits not assessed
Nadeem et al, 2013 [1]	PCT (86) vs. non-PCT (86)	68 vs. 68	COPD	HCT ≥ 50% on two occasions	53% vs. 43%	VTE 19% vs. 14% (P = 0.42) †	Well-matched groups	No data on the use of phlebotomy
Perloff et al, 1993 [2]	Comp (101) vs. Uncomp (11) PCT	36 (19 - 74)	Cyanotic CHD	HCT > 45%	57% vs. 69%	Stroke 0% ‡	High-risk patients with hyperviscosity symptoms; long follow-up	Phlebotomy at 3 - 6 months interval for symptom relief (20% vs. 80%)
Schwarcz et al, 1993 [5]	SP (27) vs. PV (43)	55 vs. 59	Smoking vs. PV	Increased RBC volume	59% vs. 59%	Arterial or venous thrombosis 41% vs. 60% (P < 0.05) §	PV is more hypercoagulable than SP	Diagnostic criteria, smoking as a confounder
Lubarsky et al, 1991 [3]	PCT (100) vs. non-PCT (100)	57 vs. 60	COPD	Hgb > 16 g/dL	Hgb 17 vs. 13 g/dL	Arterial or venous thrombosis 0% vs. 3%; (P = NS)	No thrombotic complications even during surgery	Follow-up limited to 30 days postoperatively; significant postoperative blood loss in 25% patients with PCT

Table 1. Secondary Polycythemia and the Risk of Venous Thromboembolism in Adults

Author, year

Study groups (N)

Age in years

Etiology of PCT

Definition of PCT

Average HCT

Outcomes

Strength

Limitation

CHD: congenital heart disease; Comp: compensated; COPD: chronic obstructive pulmonary disease; DVT: deep venous thrombosis; HCT: hematocrit; Hgb: hemoglobin; N: number of patients; NS: not significant; PCT: polycythemia; PE: pulmonary embolism; PV: polycythemia vera; RBC: red blood cell; SP: secondary polycythemia; Uncomp: uncompensated; VTE: venous thromboembolism. All studies, except by Ristic et al [4], were retrospective. *The study included patients who presented with respiratory distress, and were found to have elevated D-dimer. †Obesity was identified as a possible risk factor for venous thromboembolism in secondary polycythemia. ‡A 28-year-old female with iron-deficient polycythemia had four episodes of amaurosis fugax during few months when hematocrit level ranged between 63% and 73%. §In smoking-related secondary polycythemia, there was only one venous thromboembolism and 11 arterial events (myocardial infarction, stroke or transient ischemic attacks). Risk of venous thromboembolism was 4% vs. 21% in secondary polycythemia compared to polycythemia vera. The incidence of recurrent events was higher in polycythemia vera compared to secondary polycythemia (28% vs. 7%). Within secondary polycythemia, patients who had an event had lower hematocrit and platelet count than those who did not have an event.

Ristic et al, 2013 [4]

PCT (100) vs. non-PCT (262)

66 vs. 63

COPD/respiratory failure

HCT > 50%

58% vs. 40%

PE 39% vs. 11% (P < 0.001); DVT 5% vs. 4% (P = 0.87)

Only prospective study

Inclusion criteria,* unmatched groups, smoking habits not assessed

Nadeem et al, 2013 [1]

PCT (86) vs. non-PCT (86)

68 vs. 68

COPD

HCT ≥ 50% on two occasions

53% vs. 43%

VTE 19% vs. 14% (P = 0.42) †

Well-matched groups

No data on the use of phlebotomy

Perloff et al, 1993 [2]

Comp (101) vs. Uncomp (11) PCT

36 (19 - 74)

Cyanotic CHD

HCT > 45%

57% vs. 69%

Stroke 0% ‡

High-risk patients with hyperviscosity symptoms; long follow-up

Phlebotomy at 3 - 6 months interval for symptom relief (20% vs. 80%)

Schwarcz et al, 1993 [5]

SP (27) vs. PV (43)

55 vs. 59

Smoking vs. PV

Increased RBC volume

59% vs. 59%

Arterial or venous thrombosis 41% vs. 60% (P < 0.05) §

PV is more hypercoagulable than SP

Diagnostic criteria, smoking as a confounder

Lubarsky et al, 1991 [3]

PCT (100) vs. non-PCT (100)

57 vs. 60

COPD

Hgb > 16 g/dL

Hgb 17 vs. 13 g/dL

Arterial or venous thrombosis 0% vs. 3%; (P = NS)

No thrombotic complications even during surgery

Follow-up limited to 30 days postoperatively; significant postoperative blood loss in 25% patients with PCT