Table 3 Characteristic of samples and data of included studies

Akinori et al., 2000 [62]

Accra (Hospitalized patients) and Dodowa Community (control group), both in Ghana.

1995: Cerebral Malaria - 41, Severe Malaria – 10;

1997: Cerebral Malaria - 60, Severe Malaria - 24

3 to 12 years

CM: Unrousable coma (Blantyre Coma Score 3/4 3)

SM: Haemoglobin < 5 g/dL in fully conscious

Blood/ ELISA Kits

TNF-α levels were significantly higher in CM (147 ± [113–192]) compared to SM (87 ± [54–139]) and UM (77 ± [58–102]).

One-Way and Two-Way Parametric ANOVA following Tukey’s posthoc test. Data were considered significant when p < 0,05

Sample Armah et al., 2005 [52, 53]

Emergency Unit at the Department of Child Health - Korle-Bu Teaching Hospital, Accra, Ghana.

Cerebral Malaria – 10

Severe Malaria - 5

–

CM: Blantyre coma score of 2

SM: Haemoglobin < 5 g/dL in fully conscious

Brain (Post-Morten)/Immunostaining for TNF-alfa

TNF-α was expressed in CM brain sections in the intravascular, perivascular and intraparenchymal pattern, but none of the sections of the other group.

For each of the six antigens studied, the percentage of immunostained cases and the intensity of staining were compared between the five groups of cases and the three regions of the brain.

Cabantous et al., 2006 [54]

Gabriel Toure and Hospital in Bamako, Mali.

Cerebral Malaria – 58

Severe Malaria - 27

–

CM: Unrousable coma (Blantyre Coma Score 3/4 3)

SM: with a thick blood film positive for P. falciparum, a packed cell volume of 15%, and no impaired consciousness.

2–5 ml Blood TNF levels by ELISA.

Our analysis also failed to detect significant differences in TNF-α plasma levels between children with CM or SM and control children.

Unmatched groups were compared by using the Mann-Whitney U test (SPSS 10.1 software), with P values of < 0.05 being considered significant. The levels of TNF in the plasma of children with CM and SM were low (median 1 pg/ml) and not significantly different.

Kinra and Dutta, 2013 [31]

This was a multicentric study carried out in three hospitals simultaneously.

Cerebral Malaria – 2

Severe Malaria - 14

–

CM: were comatose and had detectable P. falciparum asexual forms in peripheral blood,

SM: Subjects with parasite index of more than 1%, blood sugar < 60 mg/dl), severe anaemia (Hb < 7 g/dl)

Plasma sample/ELISA Kits

Compared with the children with uncomplicated malaria, mean plasma TNF-α levels were twice as high in cerebral malaria survivors and ten times as high in the fatal cases.

The nonparametric test (Mann-Whitney rank-sum test) was used for TNF-α analysis. Normally distributed data were analyzed using Student’s t-test (all p values are two-tailed). Pearson’s correlation coefficient was used to evaluate the relationship within normally distributed variables. P values < 0.05 were considered significant.

Kwiatkowski et al., 1990 [28]

Royal Victoria Hospital, Banjul, The Gambia and the Medical Research Council (MRC) Laboratories, Fajara, The Gambia.

Cerebral Malaria – 110;

Middle Malaria - 178

–

CM: Coma score of 2 or less, persists for more than 30 min after any convulsions had ceased

MM: Febrile illness in a child with asexual, without other satisfactory explanation for the fever and cerebral malária.

Plasma sample/ELISA Kits

In plasma samples collected within 4 h of presentation, the geometric mean TNF-α concentration was higher in malária than in non-malaria patients and increased with the severity of malaria, levels were significantly higher in fatal CM than in non-fatal CM, in non-fatal CM than in MM.

The detection limits of these assays were: TNF- 10 pg/ml; IL-lot 10 pg/ml; and IFN-y 25 pg/ml. For statistical purposes, results below these limits were assigned values of 5 pg/ml, 5 pg/ml, and 12–5 pg/ml, respectively. Data were analyzed with the software package SPSS/PC+ v3.1.

Prakash et al., 2006 [32]

Gondia District of Maharashtra State, India.

Cerebral Malaria – 26

Severe Malaria - 33

5 to 75 years

CM: were in a comatose state

SM: were fully conscious and were able to respond well verbally to the doctors’ questions

Plasma sample/estimated by use of Opti-EIA kits

The levels of IL-1b, IL-10, TNF-α, and TGF-b were observed to be most significantly increased in the CM group, compared with those in the endemic control group or in the other groups of P. falciparum-infected patients (for all comparisons, P < 10⁻⁶).

Comparisons between groups were calculated by the Mann-Whitney rank-sum test. The significance criterion was a Bonferroni-corrected P value < 0.05. For this purpose, special macros addition to the software IgorPro (version 3.16; WaveMetrics) were used.

Sahu et al., 2013 [33]

SCB Medical College and Hospital, Cuttack, and Regional Medical Research Centre in Orissa, both in Odisha, India.

Cerebral Malaria – 52

Severe Malaria - 85

< 15 years

CM: was further defined as patients with altered sensorium, GCS (Glasgow Coma Scale) of 610

SM: hemoglobin < 5 g/dl and acute renal failure

Plasma/ ELISA Kits

Significantly elevated levels of TNF-α were noted in all the parasitemic study patients compared to control (12.51 ± 1.779 pg/ml) the highest in MOD (68.57 ± 8.617 pg/ml) followed by CM (52.40 ± 5.285 pg/ml) than the SM

Significance determined by the Kruskal–Wallis test enabled subsequent intergroup comparisons using the Mann–Whitney U test; P < 0.05 (2-tailed) was considered significant. The correlations were carried out using the Pearson’s rank test (r) to investigate the relationship between MP counts with clinical as well as biological parameters and TNF-α level. P < 0.05(a) was considered significant.

Thuma et al., 2011 [29]

Pediatric Unit of Yaound’ e Central Hospital, known as The Chantal Biya Foundation, Cameroon.

Cerebral Malaria - 28;

Severe Malaria - 72

< 6 years

CM: screening hematocrit level of > 18% and unarousable coma as defined by a Blantyre coma score of < 2

SM: screening hematocrit level of, 15% and the absence of coma

Plasma/Multiplex Immunoassay kits (LINCO Research)

In contrast to those of the children with severe malarial anemia [33.1 (12.3–96.5)], none of the plasma concentrations of the originally selected immune markers differed significantly between children with cerebral malaria [44.7 (35.6–100.4)].

Continuous variables were compared with the Kruskal-Wallis test, and categorical variables were compared with the Fisher exact test. Relationships between 2 continuous variables were assessed with the Spearman correlation coefficient.