Improved predictability is needed for calculators used to preoperatively determine the etiology of splenic masses in dogs: an external validation study of the HeLP score and T-STAT

Townes N. Hillier Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, University of Georgia, Athens, GA

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Janet A. Grimes Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, University of Georgia, Athens, GA

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Mandy L. Wallace Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, University of Georgia, Athens, GA

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Brian J. Sutherland Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, University of Georgia, Athens, GA

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Chad W. Schmiedt Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, University of Georgia, Athens, GA

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Abstract

OBJECTIVE

To assess the predictability of the hemangiosarcoma likelihood prediction (HeLP) score and the Tufts Splenic Tumor Assessment Tool (T-STAT) for hemangiosarcoma and malignancy, respectively.

ANIMALS

261 dogs undergoing splenectomy for a splenic mass.

METHODS

Medical records were retrospectively reviewed; variables for the HeLP score and T-STAT were collected, and scores were assigned. Area under the curve (AUC) was calculated for each score.

RESULTS

The HeLP score included 141 dogs; hemangiosarcoma was diagnosed in 87 (61.7%) dogs. The median cumulative HeLP score was 51 (range, 17 to 82; IQR, 39 to 58) for dogs with hemangiosarcoma and 28 (range, 0 to 70; IQR, 17 to 41) for dogs without hemangiosarcoma. The categorical HeLP score was low (28; 32.2%), medium (31; 35.6%), and high (28; 32.2%) for dogs with hemangiosarcoma and was low (41; 75.9%), medium (9; 16.7%), and high (4; 7.4%) for dogs without hemangiosarcoma. The AUC of the cumulative and categorical HeLP scores for diagnosis of hemangiosarcoma were 0.79 (95% CI, 0.71 to 0.86) and 0.73 (95% CI, 0.65 to 0.82), respectively. The T-STAT included 181 dogs. Lesions were benign in 95 (52.5%) and malignant in 86 (47.5%) dogs. The median T-STAT score was 62% (range, 5% to 98%; IQR, 36% to 77%) for dogs with malignant lesions and 38% (range, 5% to 91%; IQR, 24% to 59%) for dogs with benign lesions. The T-STAT had an AUC of 0.68 (0.60 to 0.76) for diagnosis of malignancy.

CLINICAL RELEVANCE

The HeLP score had acceptable performance, and the T-STAT had poor performance for diagnosis prediction. A tool with excellent or outstanding discrimination is needed to more reliably predict the presence of hemangiosarcoma or a malignant lesion preoperatively.

Abstract

OBJECTIVE

To assess the predictability of the hemangiosarcoma likelihood prediction (HeLP) score and the Tufts Splenic Tumor Assessment Tool (T-STAT) for hemangiosarcoma and malignancy, respectively.

ANIMALS

261 dogs undergoing splenectomy for a splenic mass.

METHODS

Medical records were retrospectively reviewed; variables for the HeLP score and T-STAT were collected, and scores were assigned. Area under the curve (AUC) was calculated for each score.

RESULTS

The HeLP score included 141 dogs; hemangiosarcoma was diagnosed in 87 (61.7%) dogs. The median cumulative HeLP score was 51 (range, 17 to 82; IQR, 39 to 58) for dogs with hemangiosarcoma and 28 (range, 0 to 70; IQR, 17 to 41) for dogs without hemangiosarcoma. The categorical HeLP score was low (28; 32.2%), medium (31; 35.6%), and high (28; 32.2%) for dogs with hemangiosarcoma and was low (41; 75.9%), medium (9; 16.7%), and high (4; 7.4%) for dogs without hemangiosarcoma. The AUC of the cumulative and categorical HeLP scores for diagnosis of hemangiosarcoma were 0.79 (95% CI, 0.71 to 0.86) and 0.73 (95% CI, 0.65 to 0.82), respectively. The T-STAT included 181 dogs. Lesions were benign in 95 (52.5%) and malignant in 86 (47.5%) dogs. The median T-STAT score was 62% (range, 5% to 98%; IQR, 36% to 77%) for dogs with malignant lesions and 38% (range, 5% to 91%; IQR, 24% to 59%) for dogs with benign lesions. The T-STAT had an AUC of 0.68 (0.60 to 0.76) for diagnosis of malignancy.

CLINICAL RELEVANCE

The HeLP score had acceptable performance, and the T-STAT had poor performance for diagnosis prediction. A tool with excellent or outstanding discrimination is needed to more reliably predict the presence of hemangiosarcoma or a malignant lesion preoperatively.

Introduction

Splenic masses are frequently discovered in canine patients and may be identified incidentally; associated with vague clinical signs such as vomiting, inappetence, and weight loss1,2; or associated with hemoperitoneum.1 Splenic masses may be either malignant or benign, with the most common diagnoses being hemangiosarcoma, nodular hyperplasia, and hematoma.3,4 Dogs diagnosed with hemangiosarcoma have a median survival time of 54 to 86 days with surgery alone and 103 to 160 days with surgery and chemotherapy, while dogs diagnosed with benign lesions are cured following splenectomy.35 This makes it challenging for owners to decide whether to move forward with surgery, as there are no sensitive or specific tests to definitively diagnose the etiology of a splenic mass prior to surgery and histopathology.

In lieu of a definitive presurgical diagnostic test, veterinarians have historically relied on the double two-thirds rule to inform owners of the prognosis for splenic lesions. This rule states that two-thirds of dogs with splenic masses have a malignancy and that two-thirds of those malignancies are hemangiosarcoma.6 More recent data show that when comparing dogs with or without hemoperitoneum, the probability of a malignancy differs. In dogs with nontraumatic hemoperitoneum, 73% of dogs have a malignant mass, and of those malignancies, 87% are due to hemangiosarcoma.7 Contrarily, 70% of dogs with splenic masses without hemoperitoneum have benign lesions.2

Recently, 2 scoring systems were developed to predict the odds of either hemangiosarcoma in dogs with spontaneous hemoperitoneum or a malignant lesion in dogs with splenic masses.8,9 Both scores report an area under the curve (AUC) for the receiver operating characteristic curve, which allows for comparison of the scoring systems.10 The receiver operating characteristic curve plots the true positive rate against the false positive rate, and the AUC summarizes the diagnostic accuracy of a test. An AUC of 1 represents perfect accuracy between conditions, an AUC of 0 represents perfect inaccuracy between conditions, and an AUC of 0.5 indicates the test is unable to discriminate between conditions.10 The hemangiosarcoma likelihood prediction (HeLP) model was developed for dogs with nontraumatic hemoperitoneum from any organ and uses patient body weight, admission total plasma protein, admission platelet count, and thoracic radiograph findings to assign dogs a low, medium, or high risk of having hemangiosarcoma.8 This 4-variable model had an AUC of 0.85 for the model development group (219 dogs) and 0.77 for the validation group (187 dogs).8 A second prediction calculator, the Tufts Splenic Tumor Assessment Tool (T-STAT), was developed to estimate the probability of malignancy in dogs with splenic lesions with or without hemoperitoneum.9 This model uses 8 variables from bloodwork and abdominal ultrasound (serum total protein, number of nucleated RBCs/100 WBCs, splenic mass diameter, number of liver nodules, number of splenic nodules, splenic mass inhomogeneity, volume of abdominal effusion, and the presence of mesenteric, omental, or peritoneal nodules) to determine the probability of a malignant lesion. The AUC for this model was 0.80 for the model development group (422 dogs) and 0.78 for the validation group (100 dogs).9 Both groups recommend use of each calculator in conjunction with the overall clinical picture and not as the sole basis for decision-making.

The objective of this study was to assess the ability of the HeLP score and T-STAT to correctly predict the diagnosis (hemangiosarcoma or malignant lesion, respectively) in an external validation group of dogs undergoing splenectomy for a splenic mass at an academic referral center.

Methods

Medical records of all dogs undergoing a splenectomy from January 2015 through July 2023 at the University of Georgia Veterinary Teaching Hospital were reviewed. Dogs were excluded if information required for the HeLP score or T-STAT was not available in the record and may have been excluded from one or the other model or both depending upon the available data. Data collected from the medical record for all dogs included signalment (breed, age, body weight, sex, reproductive status), date of presentation, reason for presentation, the presence of hemoperitoneum, and histopathologic diagnosis of the spleen.

Dogs were included in the HeLP score group only if hemoperitoneum was confirmed by fluid analysis or surgery report. Data collected for this score were body weight, plasma protein, platelet count, and thoracic radiograph findings. Dogs were assigned a score for each variable, as previously described.9 Briefly, dogs weighing < 35.1 kg received a score of 0, those weighing between 35.1 and 42 kg received a score of 12, and those weighing > 42 kg received a score of 14. The score assigned for total solids was 10 for < 5.3 g/dL, 15 for 5.3 to 5.8 g/dL, 23 for 5.9 to 6.2 g/dL, and 0 for > 6.2 g/dL. The score assigned for platelet count was 26 for < 60 X 109/L, 24 for 60 to 114 X 109/L, 27 for 115 to 134 X 109/L, and 0 for > 134 X 109/L. Dogs with normal thoracic radiographs or that did not have radiographs available received a score of 17; if the radiographs were abnormal but did not show a metastatic pattern, a score of 0 was given; and if there was an abnormal lung pattern consistent with metastatic disease, a score of 36 was given. The score for each variable was summed (cumulative HeLP score), and dogs were then assigned to 1 of 3 groups (categorical HeLP score) based on the total sum, as previously described: low risk (0 to 40), medium risk (41 to 55), and high risk (> 55) for the diagnosis of hemangiosarcoma.8

Dogs with or without hemoperitoneum were included in the T-STAT group, and data collected were serum total protein concentration (rounded to the nearest whole number), number of nucleated RBCs/100 WBCs (0/1 or ≥ 2), splenic mass diameter (largest dimension), number of liver nodules (0, 1, > 1), number of splenic masses (1 or > 1), the degree of inhomogeneity of the mass (none/mild or moderate/marked), the volume of abdominal effusion (none/mild or moderate/marked), and the presence of mesenteric, omental, or peritoneal nodules.9 Variables requiring diagnostic imaging were recorded from the ultrasound or CT report. If variables were not reported in the diagnostic imaging report, the images were reviewed directly to determine the value using previously established guidelines.9 Variables were input into the online prediction calculator (t-stat.org), which assigned each dog a percentage likelihood for malignancy ranging from 0% to 100%.

Statistical analysis

Statistical analysis was performed with JMP Pro, version 17.0.0 (SAS Institute Inc; descriptive statistics) and IBM SPSS Statistics for Windows, version 28.0.0.0 (IBM Corp; AUC and 95% CI). Data were tested for normality via visual inspection of the histogram and normal quantile plot. Descriptive data were generated, with normally distributed data reported as mean ± SD and nonnormally distributed data reported as median (range) or median (range and IQR). Nominal logistic regression was used to determine the AUC for the cumulative HeLP score and categorical HeLP score versus a diagnosis of hemangiosarcoma and for the T-STAT versus a diagnosis of a malignant or benign lesion. Interpretation of the AUC was performed via a previously described scale with 0.5 indicating no discrimination, 0.5 to 0.7 indicating poor discrimination, 0.7 to 0.8 indicating acceptable discrimination, 0.8 to 0.9 indicating excellent discrimination, and > 0.9 indicating outstanding discrimination.10

Results

A total of 427 dogs that underwent splenectomy from January 2015 through July 2023 were identified. One hundred sixty-four dogs were excluded due to missing 1 or more necessary values required for the prediction calculators, resulting in a final number of 141 dogs for the HeLP score and 181 dogs for the T-STAT. Fifty-nine dogs were included in both calculators.

HeLP score

One hundred forty-one dogs had all variables required for the HeLP score, including hemoperitoneum confirmed via fluid analysis or as noted in the surgery report. The mean age at time of splenectomy was 10.1 ± 2.1 years, and there were 81 males (57.4%; 71 castrated, 10 intact) and 60 females (42.6%; 59 spayed, 1 intact). There were 47 breeds represented, with mixed-breed dog (n = 40 [28.4%]), Golden Retriever (13 [9.2%]), Labrador Retriever (13 [9.2%]), German Shepherd Dog (10 [7.1%]), and American Pit Bull Terrier (9 [6.4%]) being the most common. Remaining breeds were represented by ≤ 4 dogs.

A malignant lesion was diagnosed in 100 (70.9%) dogs, and a benign lesion was diagnosed in 41 (29.1%) dogs. Hemangiosarcoma was diagnosed in 87 (61.7%) dogs. Malignancies other than hemangiosarcoma included lymphoma (n = 4), histiocytic sarcoma (2), undifferentiated sarcoma (2), and 1 each of fibrosarcoma, leiomyosarcoma, mixed mesenchymal cell neoplasm, myxoid liposarcoma, and osteosarcoma. Benign lesions were most commonly hematoma, extramedullary hematopoiesis, and lymphoid/nodular hyperplasia, often occurring in combination with each other (n = 35), myelolipoma (3), hemangioma (2), and splenitis (1).

The calculator variables and resultant HeLP scores were recorded (Table 1). The cumulative HeLP score had an AUC of 0.79 (95% CI, 0.71 to 0.86; Figure 1), and the categorical HeLP score had an AUC of 0.73 (95% CI, 0.65 to 0.82; Figure 2) for a diagnosis of hemangiosarcoma.

Table 1

Variables used to determine the likelihood of hemangiosarcoma and resultant hemangiosarcoma likelihood prediction (HeLP) score for 141 dogs with nontraumatic hemoperitoneum that underwent splenectomy for a splenic mass.

Variable All dogs (n = 141) Dog without HSA (n = 54) Dogs with HSA (n = 87)
Weight (kg) 28 (5–68) 26 (5–52) 30 (6–68)
Total plasma protein (g/dL) 6 (2.6–9.6) 6.7 (4.3–9.6) 6 (2.6–8.2)
Platelet count (X 109/L) 122 (18–822) 224 (31–822) 93 (18–414)
Thoracic radiographs
  Normal 112 (79.4%) 39 (72.2%) 73 (83.9%)
  Abnormal, no metastasis 18 (12.8%) 9 (16.7%) 9 (10.3%)
  Not available 7 (5.0%) 5 (9.3%) 2 (2.3%)
  Abnormal, metastasis 4 (2.8%) 1 (1.9%) 3 (3.4%)
HeLP score
  Cumulative 41 (0–82) 28 (0–70; 17–41) 51 (17–82; 39–58)
  Low 69 (48.9%) 41 (75.9%) 28 (32.2%)
  Medium 40 (28.4%) 9 (16.7%) 31 (35.6%)
  High 32 (22.7%) 4 (7.4%) 28 (32.2%)

Results are reported as median (range) or median (range; IQR) for continuous variables or number (%) of dogs for categorical variables.

HSA = Hemangiosarcoma.

Figure 1
Figure 1

Receiver operating characteristic curve for the cumulative hemangiosarcoma likelihood prediction (HeLP) score in 141 dogs with nontraumatic hemoperitoneum that underwent splenectomy for a splenic mass (area under the curve, 0.79; 95% CI, 0.71 to 0.86). The 45° diagonal line represents no discrimination between groups.

Citation: Journal of the American Veterinary Medical Association 262, 7; 10.2460/javma.24.01.0016

Figure 2
Figure 2

Receiver operating characteristic curve for the categorical hemangiosarcoma likelihood prediction (HeLP) score in 141 dogs with nontraumatic hemoperitoneum that underwent splenectomy for a splenic mass (area under the curve, 0.73; 95% CI, 0.65 to 0.82). The 45° diagonal line represents no discrimination between groups.

Citation: Journal of the American Veterinary Medical Association 262, 7; 10.2460/javma.24.01.0016

T-STAT

One hundred eighty-one dogs had all variables required for the T-STAT. The mean age at diagnosis was 10.7 ± 2.3 years, and the median body weight was 25 kg (range, 3 to 77 kg). There were 107 males (59.1%; 90 castrated, 17 intact) and 74 females (40.9%; 73 spayed and 1 intact). There were 50 breeds represented, with mixed-breed dog (53 [29.3%]), Labrador Retriever (22 [12.2%]), and Golden Retriever (11 [6.1%]) being the most common. Remaining breeds were represented by ≤ 7 dogs. One hundred fifty-eight dogs underwent ultrasound, 23 underwent CT, and 1 underwent MRI.

A benign lesion was diagnosed in 95 (52.5%) dogs, and a malignant lesion was diagnosed in 86 (47.5%) dogs. Hemangiosarcoma was diagnosed in 59 (32.6%) dogs. Malignancies other than hemangiosarcoma included lymphoma (n = 14), histiocytic sarcoma (4), leiomyosarcoma (2), and 1 each of fibrosarcoma, myxoid liposarcoma, stromal sarcoma, soft tissue sarcoma, undifferentiated sarcoma, metastatic adenocarcinoma, and metastatic gastrointestinal stromal cell tumor or leiomyosarcoma. Benign lesions were most commonly hematoma, extramedullary hematopoiesis, lymphoid/nodular hyperplasia, and/or infarct often occurring in combination with each other (n = 75). Other benign lesions were myelolipoma (n = 5), congestion (4), lipoma (4), hemangioma (3), splenitis (2), and 1 each of splenic abscess and splenitis with bacteria.

The calculator variables and resultant T-STAT score were recorded (Table 2). The T-STAT had an AUC of 0.68 (95% CI, 0.60 to 0.76; Figure 3) for diagnosis of a malignant lesion.

Table 2

Variables used to determine the likelihood of a malignant lesion and resultant Tufts Splenic Tumor Assessment Tool (T-STAT) score for 181 dogs that underwent splenectomy for a splenic mass.

Variable All dogs (n = 181) Dogs with benign masses (n = 95) Dogs with malignant masses (n = 86)
Serum total protein (g/dL) 7 (2–10) 7 (4.8–9) 6 (2–10)
Splenic mass diameter (cm) 6 (1–32) 6 (1–27) 7 (1–32)
nRBCs/100 WBCs
  0–1 140 (77.3%) 79 (83.2%) 61 (70.9%)
  ≥ 2 41 (22.7%) 16 (16.8%) 25 (29.1%)
Liver nodules
  0 122 (67.4%) 60 (63.2%) 62 (72.1%)
  1 16 (8.8%) 7 (7.4%) 9 (10.5%)
  > 1 43 (23.8%) 28 (29.5%) 15 (17.4%)
Splenic masses
  1 105 (58.0%) 61 (64.2%) 44 (51.2%)
  > 1 76 (42.0%) 34 (35.8%) 42 (48.8%)
Inhomogeneity
  None/mild 56 (30.9%) 36 (37.9%) 20 (23.3%)
  Moderate/marked 125 (69.1%) 59 (62.1%) 66 (76.7%)
Abdominal effusion
  None/mild 142 (78.5%) 83 (87.4%) 59 (68.6%)
  Moderate/marked 39 (21.5%) 12 (12.6%) 27 (31.4%)
Mesenteric/omental/peritoneal nodules
  Present 9 (5.0%) 4 (4.2%) 5 (5.8%)
  Not present 172 (95.0%) 91 (95.8%) 81 (94.2%)
T-STAT score (%) 48 (5–98) 38 (5–91; 24–59) 62 (5–98; 36–77)

Results are reported as median (range) or median (range; IQR) for continuous variables or number (%) of dogs for categorical variables.

nRBCs = Nucleated RBCs.

Figure 3
Figure 3

Receiver operating characteristic curve for the Tufts Splenic Tumor Assessment Tool (T-STAT) in 181 dogs that underwent splenectomy for a splenic mass (area under the curve, 0.68; 95% CI, 0.60 to 0.76). The 45° diagonal line represents no discrimination between groups.

Citation: Journal of the American Veterinary Medical Association 262, 7; 10.2460/javma.24.01.0016

Dogs included in both the HeLP score and the T-STAT

Fifty-nine dogs were included in both the HeLP score and the T-STAT. A malignant lesion was diagnosed in 40 (67.8%), and a benign lesion was diagnosed in 19 (32.2%) dogs. Hemangiosarcoma was diagnosed in 33 (55.9%) dogs, with the remaining malignancies being lymphoma (n = 2) and 1 each of fibrosarcoma, histiocytic sarcoma, leiomyosarcoma, myxoid liposarcoma, and undifferentiated sarcoma. Benign lesions were most commonly hematoma, extramedullary hematopoiesis, and lymphoid/nodular hyperplasia, often occurring in combination with each other (n = 17), and 1 each of hemangioma and splenitis.

The resultant HeLP and T-STAT scores were recorded (Table 3). The cumulative HeLP score had an AUC of 0.72 (95% CI, 0.59 to 0.86; Figure 4), and the categorical HeLP score had an AUC of 0.69 (95% CI, 0.55 to 0.83) for a diagnosis of hemangiosarcoma. The T-STAT had an AUC of 0.64 (95% CI, 0.49 to 0.78) for a diagnosis of a malignant lesion.

Table 3

The hemangiosarcoma likelihood prediction (HeLP) and Tufts Splenic Tumor Assessment Tool (T-STAT) scores for 59 dogs with splenic masses that met the inclusion criteria for both the HeLP score and T-STAT.

Variable All dogs (n = 59) Dogs without HSA (n = 26) Dogs with HSA (n = 33)
HeLP score
Cumulative 43 (15–72) 32 (15–70; 17–51.5) 51 (17–72; 37–61)
Low 26 (44.1%) 17 (65.4%) 9 (27.3%)
Medium 19 (32.2%) 5 (19.2%) 14 (42.4%)
High 14 (23.7%) 4 (15.4%) 10 (30.3%)
All dogs (n = 59) Dogs with benign masses (n = 19) Dogs with malignant masses (n = 40)
T-STAT score (%) 67 (9–98) 60 (19–91; 53–69) 72 (9–98; 50–85)

Results are reported as median (range) or median (range; IQR) for continuous variables or number (%) of dogs for categorical variables. HSA = Hemangiosarcoma.

Figure 4
Figure 4

Receiver operating characteristic curve for the cumulative hemangiosarcoma likelihood prediction (HeLP) score (A; area under the curve, 0.72; 95% CI, 0.59 to 0.86), categorical HeLP score (B; area under the curve, 0.69; 95% CI, 0.55 to 0.83), and Tufts Splenic Tumor Assessment Tool (T-STAT) (C; area under the curve, 0.64; 95% CI, 0.49 to 0.78) in 59 dogs that underwent splenectomy for a splenic mass that met the inclusion criteria for both the HeLP score and T-STAT. The 45° diagonal line represents no discrimination between groups.

Citation: Journal of the American Veterinary Medical Association 262, 7; 10.2460/javma.24.01.0016

Discussion

In this population of dogs, the cumulative HeLP score had an AUC of 0.79, and the categorical HeLP score had an AUC of 0.73 for a diagnosis of hemangiosarcoma, which is considered acceptable performance. This is similar to the AUC of 0.77 found in the validation group for the categorical HeLP score, although it remains less than the AUC of 0.85 found in the model development group.8 The T-STAT had an AUC of 0.68 for the diagnosis of a malignant lesion, which is considered poor performance. This is less than that reported for both the model development group (AUC, 0.80) and the validation group (AUC, 0.78).9

For the HeLP score, the cumulative score had a higher AUC compared to the categorical AUC, possibly due to dogs at the extremes of each categorical score being incorrectly categorized. It may be more discriminatory to use the cumulative score for this calculator. Additionally, this finding may indicate that caution should be used with dogs on the extremes of each categorical score, as they may be more likely to be miscategorized. In this external validation group, the HeLP score appeared to better predict a diagnosis other than hemangiosarcoma, as 75.9% of dogs without hemangiosarcoma were correctly classified as having a low risk of hemangiosarcoma. Conversely, dogs with hemangiosarcoma were more evenly spread across the risk categories (32.2% classified as low risk, 35.6% classified as medium risk, and 32.2% classified as high risk). One factor that may affect this is the score assigned for platelet count. In this calculator, dogs with a platelet count > 134 X 109/L are assigned a score of 0, while the other 3 categories have a similar score (26 for < 60 X 109/L, 24 for 60 to 114 X 109/L, and 27 for 115 to 134 X 109/L). A platelet count < 90,000 has been shown to have a positive predictive value of 92% for hemangiosarcoma, but a negative predictive value of only 42%.11 This is likely because a low platelet count more likely represents severe hemorrhage, rather than a specific diagnosis. Dogs with hemangiosarcoma are more likely to have hemorrhage than dogs with other diagnoses, so while use of platelet count may help to accurately classify some dogs, platelet count is a nonspecific marker, as dogs with diagnoses other than hemangiosarcoma may also have hemorrhage, and only dogs with hemorrhage are included in this calculator.7

Comparison of these calculators is challenging, as they evaluate 2 different outcomes (hemangiosarcoma for the HeLP score and malignant versus benign for the T-STAT). When comparing dogs that had both a HeLP score and T-STAT, the cumulative HeLP score had acceptable performance, with an AUC of 0.72. Both the categorical HeLP score (AUC, 0.69) and the T-STAT (AUC, 0.64) had poor discrimination in this population. The T-STAT may be less effective in accurately distinguishing between dogs with malignant lesions and those without, compared to the HeLP score's ability to predict hemangiosarcoma. This may be due to the variables that each calculator uses in its evaluation. Splenic mass size, included in the T-STAT, has been shown to discriminate between splenic mass etiologies.12 Mass-to-splenic volume ratio is smaller in dogs with hemangiosarcoma compared to those with either benign lesions or malignancies other than hemangiosarcoma; however, there is no difference in the mass-to-splenic volume ratio between dogs with benign masses and other malignant masses. Because the T-STAT only predicts malignant versus benign, combining hemangiosarcoma and other malignancies into 1 group may make the variable of splenic size less discriminatory. Additionally, in the evaluation of potentially predictive variables to develop the T-STAT, there was a small difference in splenic mass diameter between dogs with benign masses (8.8 ± 5.9 cm) and those with malignant masses (7.8 ± 4.6 cm) with a large SD; a cutoff of 7 cm was used and was significant in the final multivariable model. The T-STAT also includes the number of hepatic nodules in the model, which may negatively impact its predictability. In 1 study13 of 79 dogs with splenic hemangiosarcoma, only 50% of dogs with gross abnormalities in the liver had metastatic lesions. In another study14 of dogs with concurrent splenic and hepatic masses, 28% of dogs with a splenic malignancy had a benign liver mass. Another group also found that the odds of malignancy did not differ between dogs with single versus multiple lesions detected throughout the abdomen on abdominal ultrasound.15 Additionally, the inclusion of dogs without hemoperitoneum may reduce the reliability of the T-STAT. There is a higher incidence of hemangiosarcoma seen in dogs with nontraumatic hemoperitoneum, potentially enhancing the accuracy of the HeLP score.7 The original report8 on the HeLP score included dogs with hemoperitoneum that were not associated with the spleen, although 86% of dogs in that study had a hemoperitoneum attributable to a splenic lesion.8 This large proportion of splenic lesions in the HeLP score may be why it remained accurate when looking exclusively at dogs with hemoperitoneum due to a splenic mass.

Although 427 dogs underwent splenectomy in the study period, 164 dogs were excluded due to missing variables needed for the calculators. Neither calculator can be used without the complete set of variables, which is a limitation of their use. For the HeLP score, the most common reason for exclusion was lack of nontraumatic hemoperitoneum, followed by lack of platelet count. It is common practice in the hospital at which these patients were treated to perform an abbreviated chemistry panel without a CBC for dogs that are presented in an emergency setting, which explains the lack of platelet count in the record that led to the exclusion of dogs for this calculator. One benefit of this calculator is that even though thoracic radiographs are a variable in calculating the score, dogs without thoracic radiographs can be included and are assigned the same score as those with normal thoracic radiographs. This is consistent with prior literature, which indicates that dogs with splenic hemangiosarcoma do not commonly have metastasis to the lungs at initial diagnosis. In 1 study,16 the rate of lung metastasis in dogs with splenic hemangiosarcoma was 6.7%. In another study,17 the rate of lung metastasis was 21% for dogs with splenic hemangiosarcoma without concurrent right atrial involvement. In another study4 evaluating 68 dogs with splenic hemangiosarcoma that had distant metastasis, the lungs were not one of the most common sites for metastasis, with liver and omentum being the most common sites. This shows that counting dogs without thoracic radiographs as not having metastasis may be reasonable, consistent with this calculator performing as expected.

The T-STAT allows for dogs with and without hemoperitoneum to be included, which led to an increased number of dogs that could be evaluated with this calculator. The most common reason for exclusion from this calculator was lack of nucleated RBC count, followed by lack of abdominal imaging. Although dogs that are presented without hemoperitoneum may be more likely to have a CBC performed than those with hemoperitoneum, nucleated RBC count is not always included, particularly in CBCs that do not undergo slide review. This is because analyzers are unable to differentiate nucleated RBCs from leukocytes.18 The utility of this calculator in general practice may also be limited unless there is a board-certified radiologist or someone proficient in ultrasonography available to accurately assess the variables. Because 6 of the variables in this calculator require abdominal imaging to answer, it is important to be cognizant that many of these variables may be heavily user dependent based on the experience and skill of the person performing the ultrasound. All imaging studies were evaluated by a board-certified radiologist prior to finalizing the imaging report, limiting the variability for the dogs in this study. Dogs that underwent a CT scan rather than an ultrasound were included, primarily because CT is readily available in this academic institution and is frequently chosen over abdominal ultrasound in larger-breed dogs due to the ability to better evaluate the entire abdomen, especially in the presence of a large tumor. The inclusion of CT findings in this study was deemed acceptable, as CT provides greater sensitivity due to better imaging detail. This is similar for the 1 dog that underwent an MRI.

In summary, the cumulative HeLP score performed better than the categorical HeLP score to predict hemangiosarcoma in dogs with nontraumatic hemoperitoneum due to a splenic mass, although both were considered acceptable. The T-STAT score had poor discrimination of splenic malignancy in dogs with splenic masses with or without hemoperitoneum. According to the guidelines for these calculators, they should not be relied upon as the sole basis for decision-making and should only be used in conjunction with the overall clinical picture, which is consistent with only acceptable discrimination. Development of a calculator that provides excellent or outstanding discrimination is needed to provide better predictability of the etiology of splenic masses in dogs. Incorporation of variables more specific for hemangiosarcoma or malignancy, such as use of biomarkers, and development and validation of these models in larger populations of dogs may allow for more discriminatory calculators to be created.

Acknowledgments

None reported.

Disclosures

The authors have nothing to disclose. No AI-assisted technologies were used in the generation of this manuscript.

Funding

The authors have nothing to disclose.

References

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