Journal of Vascular Medicine & Surgery

Venous thrombo-embolism (VTE) involves deep venous thrombosis (DVT), with or without pulmonary embolism (PE)-the acute complication of DVT [1]. It is frequent worldwide, affecting 5 to 10% of the population [2]. The incidence is about 1 per 1000 annually in the adult population [3]. It is the third most common cardiovascular disease after acute coronary syndrome and stroke [4,5]. It is 100 times more likely to occur in hospitalised patients [6]. It is a common complication during and after hospitalisation for an acute medical illness or surgery. Most hospitalised patients have one or more risk factors for VTE, and around 60% of people undergoing major surgery will have a DVT [7]. In the absence of adequate thrombo-prophylaxis in acutely ill patients, 10 to 20% will develop a DVT [8]. This high risk is associated with low rates of adequate thrombo-prophylaxis worldwide [9,10].

The burden of VTE has not been well characterized in Low-Middle Income (LMIC) settings, especially in sub-Saharan Africa (SSA) [11]. Few studies in tertiary urban hospitals have assessed the prevention and treatment of VTE [12,13]. The ENDORSE Africa study that assessed the risk factors and rate of thrombo-prophylaxis was conducted in urban hospitals [9]. But the burden and the rate of thrombo-prophylaxis for VTE is not known in rural areas of LMICs. These informations are needed to guide informed public health strategies. We carried out this cross-sectional descriptive study with the aim of assessing the thrombo-embolic risk, and the rate of thrombo-prophylaxis for VTE in hospitalized patients in two semi-urban and rural hospitals from Cameroon-SSA.

Ethical considerations

The institutional review board of the Faculty of Medicine and Biomedical sciences of the University of Yaounde 1 approved of this study. We carried out this study in accordance with the declarations of Helsinki [14]. We report this work according to the Standards for Reporting observational studies (STROBE) guidelines [15]. We adopted the ENDORSE methodology [9,10] for this study.

Study design and setting

Between November 2016 and April 2017, author carried out this cross-sectional descriptive study in the surgical and medical units of two Hospitals in Maroua and Meskine- in the Far North region of Cameroon. Maroua is the regional capital of the region- Savannah ecological zone. It is a semi-urban setting, with a regional Hospital that has a catchment population of about 3.5 million inhabitants. Meskine is a rural setting in the out-skirts of Maroua, with a large private Hospital. Both Hospitals received about 94.000 patients annually.

Participants

These were adults ≥ 18 years of both sexes, who were hospitalized in the medical and surgical units of these Hospitals. We excluded those treated for Venous Thrombo-Embolic (VTE) disease.

Variables

We collected socio-demographic data (age, sex, level of education, monthly income, and marital status), risk factors for VTE (Classified according to the Caprini risk assessment model for VTE) [16], and prophylaxis measures for VTE (early ambulation, anti-thrombotic stockings, low molecular weight heparin, intermittent pneumatic compression, aspirin and vitamin k antagonist). We also measured their height (m) and weight (kg), to calculate their Body Mass Index (BMI).

Procedure

We prospectively recruited hospitalized patients from their bedsides. We interviewed consenting patients (French, English, or Dialect) to obtained socio-demographic data, and risk factors for VTE. We consulted their medical records to obtain data on the admission diagnoses, type of pharmacologic thrombo-prophylaxis according to the American College of Chest Physicians (ACCP) guidelines [8], and supplementary information on risk factors for VTE, and number of days of hospitalization, contra-indications for VTE prophylaxis. We measured their height in light clothing and no shoes to the nearest 0.1 kg with an electronic weighing device (Seven star® LCD display Germany). To measure the weight of bed ridden patients we used an electronic bed scale Wunder® pl-250, whereby the participants were placed supine, and their weights recorded to one decimal place in kilograms (kg). We measured their height with a stadiometer, with no shoes to the nearest 0.5 cm. For bedridden patients, we used a measuring tape. The average of two measurements was recorded.

Working definitions

We used the Caprini risk assessment model for VTE derived from the ACCP 8^th edition risk criteria for VTE [8,16]. We classified risk factors in to: Low risk - Caprini score of 2, Moderate risk - Caprini score of 3-4, and High risk - Caprini score ≥ 5. We defined appropriate VTE prophylaxis according to the ACCP guidelines [8].

Sample size : We used the Cochrane formula for cross-sectional studies to calculate the sample size [17]. With an expected proportion of 50.4% of VTE [9], and with a precision of 5%, the estimated sample size was 384 participants.

Statistical analysis

We analyzed the data with the software IBM SPSS version 23.0. We have presented the quantitative variables as means (± standard deviation), and qualitative variables as frequencies and proportions. We compared the risk factors for VTE and the thrombo-prophylaxis strategy between the surgical and medical units using the chi-squared test. We considered a p value <0.05 to be statistically significant for the observed differences.

Participants and baseline characteristics

We recruited a total of 520 patients, of whom 238 (45.8%) were admitted in the medical units, and 282 (54.2%) were admitted in the surgical units. Their mean age was 48.8 ± 17 years (Medical unit: 57.3 ± 12.6 years versus Surgical unit: 41.6 ± 17 years, p<0.001), and ranged from 18 to 90 years. There were 296 (57%) males, and 224 (43%) females. The socio-demographic characteristics are summarized in Table 1. Most of the patients were married, in their forties, self-employed, had no formal education, and earned less than 62 dollars monthly.

Table 1: Socio-demographic characteristics of the patients.

Main results

Assessing patients for VTE risk using the Caprini risk assessment model showed that 284 (54.4%) patients were at risk for VTE-182 (64.5%) in the surgical unit, and 102 (42.8%) in the medical unit (p<0.001). The risk for VTE was seen in 165 (55.7%) males, and 119 (53.1%) females (p=0.555). The VTE risk stratification is shown in Figure 1. Overall, most patients were at high risk for VTE especially in the surgical units. Table 2 shows the admission diagnoses of those at risk for VTE. Most patients in the medical units were admitted for neurological disorders, while most patients in the medical units were admitted for orthopedic disorders. The mean duration of hospitalization for those at risk of VTE was 11.9 ± 10.6 days (range: 4 to 98 days) - surgical unit: 13.8 ± 10.9 days, and medical unit: 8.7 ± 9.3 days (p<0.001). Patients admitted in the medical units were older (mean age surgical unit: 44 ± 17 years, and mean age medical units: 60.5 ± 13.7 years, p<0.001).

Figure 1: Risk stratification for Venous Thrombo-Embolism.

Table 2: Admission diagnoses of those at risk for Venous Thrombo-Embolism.

Table 3 shows the pre-admission and admission risk factors for VTE. The most frequent pre-admission risk factors were; prolonged immobility in 55 (19.4%), obesity in 42 (14.8%), and pregnancy within 3 months in 20 (7%) patients. The most frequent risk factors during admission were; complete immobilization in 91(32%), and admitted to an Intensive Care Unit (ICU) in 26 (9.2%) patients.

Table 3: Pre-admission and Admission risk factors for Venous Thrombo-Embolism.

Figure 2 shows the pattern of anti-thrombotic prophylaxis. Of the 284 patients who were at risk for VTE, 120 (42.3%) received appropriate thrombo-prophylaxis- Medical units: 33 (32.4%), and Surgical units: 87 (47.3%) (p=0.015). Table 4 shows the thrombo-prophylaxis strategy used (adequate or in-adequate) according to the level of risk presented by the patients. Low molecular weight heparin (LMWH) was frequently used in both units. Table 5 shows the contra-indications to thromboprophylaxis in those at risk. Significant renal impairment was the most common reason for contraindication to anticoagulant therapy followed by intracranial hemorrhage and clinically relevant hepatic impairment.

Figure 2: Adequate prophylaxis strategy for Venous Thrombo-Embolism.

Table 4: Adequate and In-Adequate Thrombo-prophylaxis used.

Table 5: Contra-indications to Thrombo-Prophylaxis in those at Risk.

We carried out this cross-sectional descriptive study to assess the thrombo-embolic risk, and rate of thrombo-prophylaxis for VTE in hospitalized patients in two semi-urban and rural hospitals in the Far North region (Savannah ecological zone) of Cameroon. The risk for VTE was seen in more than half of hospitalized patients in these semi-urban and rural hospitals. Less than half of those at risk received adequate thrombo-prophylaxis. The surgical units had significantly higher VTE risk and adequate prophylaxis rate than the medical units. This high risk and low thrombo-prophylaxis was seen in poor and unemployed patients at the prime of their age (40 to 50 years), with less formal education.

The high risk burden and low rates of adequate thrombo-prophylaxis for VTE in this semi-urban and rural hospitals is comparable to that reported in urban tertiary hospitals in Africa and beyond [9-11,18]. This is however associated with high rates of younger age groups, unemployment, poverty and low level of education in this semiurban and rural population. This combination has significant health and economic implications. Besides the increase in the morbidity, the mortality is expected to be higher due to the low purchasing power of the patients, the poorly equiped hospitals (consumables, materials, and personnel), and poor health system (no health coverage). The exact burden of VTE is not known in this setting, as it may go undiagnosed and under-reported [11]. It is a disease condition that is largely underdiagnosed and under-treated despite the very high disease burden in hospitalized patients worldwide [6]. Up to 60% of patients undergoing surgery will have VTE, and 10 to 20% of patients with an acute illness will have VTE [7,8]. Looking at the risk category, most of the patients had high risk for VTE. Thus, the burden of VTE is expected to be higher (more than 20%) in patients with an acute illness in this setting. This can go undiagnosed as it is often asymptomatic, or present as prolong fever mimicking an infectious process, or presents as sudden death from fatal pulmonary embolism [19]. The economic burden is expected to be high as most patients at high risk are young and potentially productive. This stress the need for adequate thrombo-prophylaxis in these settings.

Patients admitted in the medical unit were significantly older than those admitted in the surgical unit. This age pattern was similarly reported in other studies [9,10,18]. However, patients in this study were younger in both units compared to that reported by other authors [9,10,18]. We included patients from the medical units as young as 18 years compared to 40 years in other reports. Patients in the medical units were admitted for complications of chronic conditions like hypertension, which comes with age, while patients admitted in the surgical units have more acute conditions like trauma. Neurological disorders-mainly stroke syndromes, were the most frequent reasons for admission in the medical units, followed by chronic heart failure. This is consistent with other reports [9,10,18]. The pattern of admission in the surgical unit was quite different from other reports in the urban settings. Even-though orthopaedic surgery cases were frequent, most of the cases were trauma related from armed conflicts (terrorist attacks), and motorcycle accidents (frequent mode of transportation). Patients admitted in the surgical units had significantly higher rates of risk for VTE. This trend has been reported in the urban settings. The spectrum of disease is different between the units. Overall, the rate of risk for VTE was slightly higher in the semi-urban and rural settings than in the urban settings. Cohen et al. [10] reported 51.8% of patients at risk, and Kingue et al. [9] reported 51.2%, and Goubran et al. [18] reported 39.2%. The higher rate of risk for VTE in the surgical units was associated with a higher rate of adequate thrombo-prophylaxis. This trend is consistent with other reports from the urban settings [9,10,18]. As suggested by other authors, the benefits of thrombo-prophylaxis in surgical patients has long been recognized. The risk assessment for VTE is much more easier in the surgical units, as this depends on the type of surgery. The risk assessment in the medical units depends on an array of diseases and risk factors. Also, the main drivers of underuse of adequate thrombo-prophylaxis were due to medical conditions such as significant renal and liver impairment. This trend is similar to that reported by other authors [9].

Our findings should be considered in the light of some limitations due to the cross-sectional design. We assessed the use of thromboprophylaxis, but it was difficult to ascertain the quality in the short term-how many people were event free. Our findings could be overestimates of adequate thrombo-prophylaxis in this setting.

We could not assess the burden of the genetic pre-dispositions to VTE due to technical and financial constraints. Despite these limitations, this is the first study of its kind in this setting. We prospectively collected data mainly through clinical evaluation at the bedside of patients, thus ensuring high data quality. The two hospitals involved in the study are the main hospitals in the region. This study might reflect best practice in the region.

The risk for VTE was seen in more than half of hospitalized patients in these semi-urban and rural hospitals. Less than half of those at risk received adequate thrombo-prophylaxis. The surgical units had significantly higher VTE risk and adequate prophylaxis rate than the medical units. This high risk and low thromboprophylaxis was seen in poor patients, with less formal education. In order to reduce morbidity and mortality associated with VTE in low-income settings, there is a need to continuously empower the healthcare personnel in assessing the risk for VTE, and to use adequate thrombo-prophylaxis strategies. There is also the need to strengthen health system by ensuring the constant supply of lowmolecular weight heparin, and graduated compression stockings at affordable prices.

B Hamadou, F Kamdem, H Bessong, S Ndongo Amougou, L Kuate Mfeukeu contributed to the study concept and protocol. Hamadou, F Kamdem, H Bessong and S Kingue performed statistical analyses. H Bessong, CN Nganou, J Boombhi, A Menanga contributed to data acquisition. H Bessong, S Ndongo Amougou, L Kuate Mfeukeu, CN Nganou, J Boombhi, A Menanga and S Kingue analyzed and interpreted data. B Hamadou, F Kamdem, H Bessong drafted the final manuscript. All the authors approved of the final draft to be published.

We thank Dr. Ahmadou Musa Jingi (MD, DES Internal Medicine) for critically reviewing this work.